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1700/1750 RAM Expansion Module Users Guide
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The Project 64 etext of the ~1700/1750 RAM Expansion Module User's
Guide~, converted to etext by Frank Kontros <frank@kontr.uzhgorod.ua>.
1700RE10.TXT, November 1997, etext #302#
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1700/1750 RAM Expansion Module
User's Guide
For Your Commodore 128
Copyright (c) 1985 Commodore Electronics Limited
All rights reserved
This manual contains copyrighted and proprietary information. No
part of this publication may be reproduced, stored in a retrieval
system, or transmitted in any form or by any means, electronic,
mechanical, photocopying, recording or otherwise, without the
prior written permission of Commodore Electronics Limited.
This software product is copyrighted and all rights reserved by
Commodore Electronics Limited. The distribution and sale of this
product are intended for the use of the original purchaser only.
Lawful users of these programs are hereby licensed only to read
the programs, from their medium into memory of a computer, solely
for the purpose of executing the programs. Duplicating, copying,
selling or otherwise distributing this product is a violation of
the law.
DISCLAIMER
COMMODORE ELECTRONICS LIMITED ("COMMODORE") MAKES NO WARRANTIES,
EITHER EXPRESSED OR IMPLIED, WITH RESPECT TO THE PROGRAMS
DESCRIBED HEREIN, THEIR QUALITY, PERFORMANCE, MERCHANTABILITY, OR
FITNESS FOR ANY PARTICULAR PURPOSE. THESE PROGRAMS ARE SOLD "AS
IS". THE ENTIRE RISK AS TO THEIR QUALITY AND PERFORMANCE IS WITH
THE BUYER. SHOULD THE PROGRAMS PROVE DEFECTIVE FOLLOWING
PURCHASE, THE BUYER (AND NOT THE CREATOR OF THE PROGRAMS,
COMMODORE, THEIR DISTRIBUTORS OR THEIR RETAILERS) ASSUMES THE
ENTIRE COST OF ALL NECESSARY DAMAGES. IN NO EVENT WILL
COMMODORE BE LIABLE FOR DIRECT, INDIRECT, INCIDENTAL OR
CONSEQUENTIAL DAMAGES RESULTING FROM ANY DEFECT IN THE PROGRAMS
EVEN IF IT HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
SOME LAWS DO NOT ALLOW THE EXCLUSION OR LIMITATION OF IMPLIED
WARRANTIES OR LIABILITIES FOR INCIDENTAL OR CONSEQUENTIAL
DAMAGES, SO THE ABOVE LIMITATION OR EXCLUSION MAY NOT APPLY.
Commodore 128 is trademark of Commodore Electronics Limited.
CP/M is a registered trademark of Digital Research, Inc.
dBaseII is a registered trademark of Ashton-Tate, Inc.
Contents
1. INTRODUCTION
1.1. What a RAM Expansion Module Is
1.2. Two Ways to Use the RAM Expansion Module
1.3. What Comes With Your RAM Expansion Module
1.4. Suggestions on Reading This Guide
2. INSTALLATION AND DEMONSTRATION PROGRAMS
2.1. Installing the RAM Expansion Module
2.2. Using the Demonstration Programs
Booting the Demonstration Disk
Using the STARTUP Menu
3. HOW TO USE THE RAM EXPANSION MODULE IN CP/M MODE
3.1. Booting CP/M
3.2. Using CP/M Commands
4. HOW TO USE THE RAM EXPANSION MODULE IN C128 MODE
4.1. Basic Commands
4.2. Memory Locations
4.3. Example Programs
5. TECHNICAL SPECIFICATIONS
5.1. Operating Modes
5.2. Direct Memory Access Operation
5.3. Special Features
Autoload
Address Control
Interrupts
5.4. Operation Description
5.5. Timing
5.6. Bank Configuration
1. INTRODUCTION
1.1. WHAT A RAM EXPANSION MODULE IS
A RAM expansion module is a device that allows you to increase
the available memory of your computer. Your computer has two
kinds of memory areas, RAM and ROM. RAM, short for Random Access
Memory, is for temporary storage. You can put programs or other
data in RAM and retrieve them later. ROM, or Read Only Memory,
stores the operating system of your computer and may not be
changed. The 1700 and 1750 RAM expansion modules contain RAM, in
an arrangement called banks.
The 1700 RAM expansion module increases the memory of your
Commodore 128 computer by 128 Kilobytes or K (for a total of
256K). The RAM space is arranged in two 64K banks. The 1750 RAM
expansion module increases the available memory by 512K (for a
total of 640K). In the 1750 RAM Expansion Module there are eight
64K banks. All the instructions for using the two RAM expansion
modules are the same. The only difference between the two modules
is the amount of RAM they contain.
The RAM expansion module gets attached directly to your
computer's expansion port. Once installed, you give instructions
which access the expansion RAM banks. The data can be transferred
immediately from the RAM expansion module into the C128
computer's main memory. No time is lost waiting for a disk drive
to find and load a file. In CP/M mode of the C128 computer, for
example, file loading is 10 to 15 times faster with the RAM
expansion module than with a conventional disk drive.
The RAM expansion module contains indirectly accessible RAM. This
means that programs stored in the RAM expansion module cannot be
executed by the C128 computer until they are transferred from the
RAM expansion module into your computer's main memory. The main
advantage of the RAM expansion module is rapid retrieval of data.
Remember, RAM is not permanent storage. If you turn your computer
off any data stored in the RAM expansion module will be lost. Any
information stored in the RAM expansion module should therefore
also be saved on disk, to avoid loss of your work.
1.2. TWO WAYS TO USE THE RAM EXPANSION MODULE
You can use the RAM expansion module in two ways:
1) IN CP/M MODE
2) IN C128 MODE
The techniques used to access the RAM expansion module in each of
the two modes are different, but the end result is the same --
you get extra memory.
IN CP/M MODE, the RAM expansion module acts exactly like a very
rapid disk drive. Large application programs, such as word
processors or business analysis programs, can be stored in the
RAM expansion module at the beginning of a work session. From
then on, you indicate to the computer to find program utilities
in the RAM, rather than on an external disk drive. Because the
RAM expansion module stores the programs in a form the computer
can use almost instantly, operation of these programs is rapid
and efficient. You will find this ability particularly time-
saving with programs that access the disk drive often, called
"disk intensive" programs, such as dBaseII.
The CP/M system controls the RAM expansion module. You do not
have to be concerned with the way data is being stored, or where
in the RAM banks of the RAM module a particular utility is
stored. CP/M remembers all this for you, and can display a
directory of currently stored programs or data files.
IN C128 MODE, you use BASIC or machine language to perform data
transfers between the main memory of your computer and the RAM
expansion module's RAM banks. Several 7.0 BASIC commands are
designed specifically to access the RAM expansion module. Machine
language is helpful in using the more advanced functions of the
RAM expansion module in C128 mode. Using the RAM expansion module
in C128 mode requires the user to remember what has been stored
in the RAM expansion module, and where in the RAM banks the data
lies.
1.3. WHAT COMES WITH YOUR RAM EXPANSION MODULE
Along with your RAM expansion module and this manual are two
disks.
One disk contains a BASIC diagnostic test for your RAM expansion
module and several demonstration programs. This disk is
provided so you can be assured that your device operates
according to its design.
The second disk is a CP/M system disk that supports the RAM
expansion module. You may need to use this disk to boot CP/M when
you plan to use the RAM expansion module. See Chapter 3, How to
Use the RAM Expansion Module in CP/M Mode, for complete
information about this disk.
1.4. SUGGESTIONS ON READING THIS GUIDE
Here is a brief description of what is contained in the remaining
chapters of this guide:
Chapter 2 -- INSTALLATION AND DEMONSTRATION PROGRAMS gives
illustrated step-by-step instructions for installing the RAM
expansion module and describes how to use the test program and
demonstrations provided.
Chapter 3 -- HOW TO USE THE RAM EXPANSION MODULE IN CP/M MODE
contains instructions on how to determine which CP/M system disk
you should use and explains how to use the RAM module with CP/M.
Chapter 4 -- HOW TO USE THE RAM EXPANSION MODULE IN C128 MODE
describes the BASIC commands SWAP, STASH, and FETCH and shows
how to use a memory map to keep track of information stored in
the RAM expansion module.
Chapter 5 -- TECHNICAL SPECIFICATIONS; this section provides
information for advanced users.
+---------------------------------------------------------------+
| Note: It is important to read and follow the installation |
| instructions in Chapter 2. Even if you intend to use the RAM |
| expansion module in CP/M, run the diagnostic test and demo |
| programs. |
+---------------------------------------------------------------+
2. INSTALLATION AND DEMONSTRATION PROGRAMS
2.1. INSTALLING THE RAM EXPANSION MODULE
1) Turn off your computer and any peripherals.
2) Carefully remove your RAM expansion module from its protective
foam packaging. Locate the connector on the edge of the
device. See Figure 2-1.
+------------------------------+
| |
| C= 1750 RAM EXPANSION |
| |
|==============================|
|==============================|
|==============================|
| |
| |
| |
| |
| |
| |
| |
++-------------+---------------+
| |
| [] [] [] [] | connector
| | <--
+-------------+
Figure 2-1, The RAM expansion module
3) Locate the expansion port on the back of your C128 computer
(see Figure 2-2).
__/##_##_##_##___##_##_##_##___##_##_##_##___##_##_##_##\__
|-----------------------------------------------------------|
| +----------+ ___ /-\ /-\ +-----+ +-----------+ |
| |==========| [___] \_/ \_/ [] () |\@@@/| |===========| |
+-----------------------------------------------------------+
^
|
RAM module is inserted here
Figure 2-2, C128 computer expansion port
4) Carefully insert the connector on the RAM expansion module
into the expansion port on your computer. Insert the module
firmly but do not force it, as this might damage the
connectors (see Figure 2-3.)
[ Picture Omitted ]
Figure 2-3, RAM expansion module installed
5) Turn on all your equipment. Your RAM expansion module is now
ready to use.
2.2. USING THE DEMONSTRATION PROGRAMS
Included with your RAM expansion module is a test/demonstration
disk. It contains a diagnostic program to test your RAM expansion
module to see if it is operating correctly, and demonstrations
providing an example of how you might use the RAM expansion
module to aid your BASIC programming.
+---------------------------------------------------------------+
| Note: A 40-column monitor is necessary to run the |
| demonstration programs. An 80-column monitor is sufficient |
| for the diagnostic test. |
+---------------------------------------------------------------+
BOOTING THE DEMONSTRATION DISK
1) Turn off your computer.
2) Place the disk in the drive and close the disk drive door.
3) Turn on the computer. The message BOOTING STARTUP appears on
the screen, and the program loads automatically.
Note: You can also load STARTUP by typing LOAD"STARTUP",8 and
pressing (RETURN) or by typing BOOT (RETURN).
STARTUP is a program that controls the demonstration programs.
It displays a menu of the programs on the disk. STARTUP
reboots automatically when the disk is in the drive and you
press the reset button.
USING THE STARTUP MENU
The first program on the STARTUP menu is HELP.BAS. This is a file
that explains what the other programs on the disk do.
To load HELP.BAS, choose option 1 from the STARTUP menu.
A series of information screens appears. After you read each
screen, press any key to continue. When you have read the
entire file, press the reset button. The disk will reboot, and
you will be returned to the STARTUP menu.
The second program on the STARTUP menu is RAMTEST. This is the
diagnostic test.
To load RAMTEST, choose option 2 from the STARTUP menu.
The program loads and this message appears:
RAM EXPANSION TEST SIZE = 128K (512K)
TEST IS RUNNING WHEN UPPER LEFT
LOCATION ON SCREEN IS FLICKERING.
The test takes about five minutes to run. If an error is
located, an error message appears and the test stops.
If no error is located, the message TEST COMPLETED
SUCCESSFULLY appears on the screen at the end of the test.
Press the reset button, and the STARTUP program is rebooted so
you can choose another program.
IF YOU RECEIVE AN ERROR MESSAGE, RESET THE COMPUTER AND RUN
THE PROGRAM AGAIN. IF SEVERAL REPEATED EFFORTS TO RUN THE TEST
FAIL, TAKE YOUR RAM EXPANSION MODULE BACK TO THE DEALER WHO
SOLD YOU THE MODULE.
The rest of the programs on the disk are demonstration programs.
They are described in the HELP file. Choose the corresponding
number from the STARTUP menu to load each program.
Some of the demonstration programs take several minutes to load,
but begin automatically once loaded. Some programs give you the
option of stopping (using the RUN/STOP key) then starting again
without reloading the RAM expansion module. On screen directions
describe the various options presented by each program. Pressing
the reset button will always reboot the disk and return you to
the STARTUP menu.
Once you have run the RAMTEST and seen the demonstration programs
you should be confident your RAM expansion module works. Continue
with Section 3, How To Use The RAM Expansion Module In CP/M Mode
or Section 4, How To Use The RAM Expansion Module in C128 Mode.
3. HOW TO USE THE RAM EXPANSION MODULE IN CP/M MODE
3.1. BOOTING CP/M
If you are a CP/M user, you are familiar with the CP/M system
disk packed with your C128 computer. Another version of the CP/M
system came with your RAM expansion module. The reason for two
CP/M disks is this: early releases of the CP/M software packed
with the C128 computer do not support the RAM expansion module. A
special CP/M system disk, that supports the RAM expansion module,
was prepared and packaged with your RAM expansion module.
If you purchased your computer at the same time you purchased
your RAM expansion module, it is likely that the CP/M disk
supplied with your computer supports the RAM expansion module.
Commodore 128
Personal Computer 1700/1750 RAM
_____________________ Expansion Module
|=====================| __________
|~~~~~~~~~~~~~~~~~~~~~| | C= |
|_____________________| |==========|
| #### #### #### #### | |~~~~~~~~~~|
| ############## #### | | |
| ############## #### | |__________|
| ########## | |____|
`---------------------'
_| |_ _| |_
\ / \ /
\/ \/
__________ __________
| CP/M 3.0 | | CP/M 3.0 |
| __ | May or may not | __ | Supports
| | | | support RAM | | | | RAM
| ~~ | expansion, depending | ~~ | expansion
| || | on release date | || |
~~~~~~~~~~ ~~~~~~~~~~
FIGURE 3-1, CP/M system disks
If you purchased your C128 computer earlier, and later decided to
purchase a RAM expansion module, then you will probably need to
use the version of CP/M packed with your RAM expansion module.
To determine which is the most recent version of CP/M, boot each
system using the instructions below. At the top of the screen a
title and date appears. Choose the most recent version of the
CP/M system for use with the RAM expansion module, regardless of
which machine it was packaged with.
The CP/M system packaged with your RAM expansion module is booted
the same way as your original CP/M system was booted. You have
two options:
1) Turn off the computer. Place the disk in the drive, then turn
on the computer. CP/M will boot automatically.
2) Start in C128 mode, with equipment turned on. Put the CP/M
system disk in the disk drive and type the BASIC command BOOT
(RETURN).
Once the system is booted, CP/M will function in the usual manner
with up to four external disk drives labeled A through D and the
virtual drive E. Follow the instructions in your C128 Computer
System Guide for using CP/M without the RAM expansion module.
Provided below are instructions for using the RAM expansion
module like a fifth drive.
3.2. USING CP/M COMMANDS
Once the system is loaded, you can use the RAM expansion module
like a fast external drive simply by referring to drive M (Memory
drive).
For example, to save time during a work session, you might want
to store some of the more commonly used transient utilities in
the RAM expansion module. Here is the method:
1) With the CP/M utility disk in the external drive A, type:
A> PIP M:=A:FORMAT.COM [v] (RETURN)
In this example, the PIP utility would search the disk in
drive A, locate the FORMAT.COM file, and store it in the RAM
expansion module. The [v] verifies that the transfer occurred
correctly. You can also use DIR M: to determine what is stored
in the RAM expansion module.
Any filename could be used in place of FORMAT. Be sure to use
the correct filetype in addition to the filename if necessary.
2) When the computer displays the A> prompt, the transfer is
complete. Now the FORMAT utility is stored in the RAM disk.
3) To compare the speed of execution from an external drive and
from the RAM expansion module:
Type: A>FORMAT (RETURN)
The disk drive will whirl and eventually instructions for
formatting a disk will appear on screen. Abort the format by
pressing (RETURN), then any key, then answering N to the
question, "DO YOU WANT TO FORMAT ANOTHER DISK?"
Now load the FORMAT command from the RAM expansion module:
Log on to drive M by typing M: at the A> prompt.
Type: M>FORMAT (RETURN)
Almost instantly the format command is retrieved from the RAM
expansion module and displayed on the screen. Alternately, you
can choose to execute the FORMAT command without logging to
drive M> by typing M:FORMAT at the A> prompt.
This example should illustrate how the RAM expansion module can
speed up your operations. You can copy a number of files into the
RAM expansion module with a series of PIP commands. Or copy the
entire contents of a disk:
A>PIP M:=A:*.* will copy all the files from the disk in
drive A into the RAM expansion module.
Note that a full single-sided disk holds 160K of data. If your
disk is completely full, the entire contents cannot be copied
into the 1700 RAM Expansion Module.
Once the RAM expansion module has been loaded with a program, use
of the program is no different than if the program were in an
external drive. If you are saving data files for later use,
however, you may want to save them on an external drive instead
of in the RAM expansion module.
Using the reset button does not clear the expansion RAM banks,
only the C128 computer's main memory.
To avoid accidental loss of your work, periodically save programs
or data files in progress on disk, as well as in the RAM
expansion module. A power surge, or an accidentally pulled
electric cord, can have a devastating effect on your work if you
only store it in the RAM expansion module.
4. HOW TO USE THE RAM EXPANSION MODULE IN C128 MODE
4.1. BASIC COMMANDS
There are three BASIC commands built into BASIC 7.0 that were
designed especially for use with the RAM expansion module. These
commands handle the three types of data transfers possible with
the RAM expansion module:
1) STASH - Stores data in the RAM expansion module
2) FETCH - Retrieves data stored in the RAM expansion module and
places them in main memory
3) SWAP - Exchanges data stored in the RAM expansion module with
data stored in main memory
Each of these command words is followed by four parameters that
define how large a block of data is being transferred, where in
main memory the data is currently stored, where in the RAM
expansion module (i.e. what address) the data should be
transferred, and what expansion RAM bank is being used.
The parameters are the same for all three commands:
FETCH
STASH number of bytes,intsa,expsa,expba
SWAP
where bytes = number of bytes involved in the transfer
intsa = starting address of host RAM (0 - 65535)
expsa = starting address of expansion RAM (0 - 65535)
expba = expansion RAM bank number (0 - 1 on the 1700)
(0 - 7 on the 1750)
Note: FETCH, STASH, and SWAP only accept decimal numbers.
When you use any of these commands, you are transferring blocks
of data from one area of RAM to another. It is important that you
know what you are transferring, and where you are putting it. If
you transfer data into an area that already is occupied by a
program or other data, the data you transfer into that area will
overwrite the original data. This can have an undesired effect on
the outcome of the transfer.
4.2. MEMORY LOCATIONS
In order to guarantee a safe transfer, you need to be aware of
the memory map for your computer. It is a diagram, see Figure 4-1
on next page, that shows what each section of your computer's
memory stores. Certain areas are set aside for specific
functions, and other areas are free for your programs. The entire
contents of the RAM expansion module is up to you; no space is
preallocated.
When you perform any operation with your computer, data is stored
in your computer's memory. Each memory location is given an
address which, like the street addresses of houses, can be used
to identify a particular location. The specific contents of
memory locations determines the output of programs, what the
screen looks like, and other computer functions.
The addresses of memory locations accessible by the user range
from 0 to 65535. Many of these locations, however, have special
purposes. For example the addresses between 4608 and 4864 are
reserved for storing absolute values for BASIC programs.
One important note: the BASIC commands STASH, FETCH and SWAP can
only be used to transfer or retrieve data in Bank 0 of the C128
computer's internal RAM. See the section entitled NOTES FOR BASIC
PROGRAMMERS in Chapter 5 for details on accessing Bank 1.
The 1700 RAM expansion module contains two RAM banks labeled 0
and 1. The 1750 RAM expansion module has eight RAM banks labeled
0 to 7. All the banks in the RAM expansion modules are available
with the BASIC commands STASH, FETCH, and SWAP. The RAM expansion
module banks bear no relation to the C128 computer RAM banks.
C128 RAM Decimal Hex C128 ROM
+---------------+ 65535 FFFF +-------------+ - Kernal Jump Table & -.
| NMI RST IRQ | | | Hardware Vectors |
| CP/M RAM Code | 65357 FF4D | | |
|Kernal RAM Code| | | |
| | | | |
| | | | |
+---------------+ 65285 FF05 +-------------+ - Kernal Interrupt |
| MMU | |/////////////| Dispatch Code |
| Configuration | |/////////////| |
| Register | |/////////////| |
+---------------+ 65280 FF00 +/////////////+ - MMU Configuration |
| | | | Registers |
| | | | |
| | | | |
| | 64640 FC80 +-------------+ - ROM reserved for |~~\ HIGH
| | | | Foreign Lang.Versions|__/ ROM
| | | | |
| | | | |
| | 64128 FA80 +-------------+ - Editor Tables |
| | | | |
| | | | |
| | | | |
| | 57344 E000 +-------------+ - Kernal ROM Code |
|BASIC TEXT AREA| |/////////////| |
| (Basic text | |/////////////| |
|begins at $1C00| |/////////////| |
| if bit-map | 53248 D000 +/////////////+ - I/O Space |
| unallocated | | | |
| | | | |
| | | | |
| | 49152 C000 +-------------+ - - Editor ROM Code - -|
| | | | |
| | | | |
| | 45056 B000 +-------------+ -- Monitor ROM Code - -|
| | | | |~~\ MID
| | | | |__/ ROM
| | 32768 8000 | | - - - - - - - - - - - -|
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |~~\ LOW
| | | | |__/ ROM
+---------------+ 16384 4000 +-------------+ - - Basic ROM Code - --~
| VIC BIT-MAP |
| Screen |
+- - - - - - - -+ 8192 2000
| VIC BIT-MAP |
| Color (VM#2) |
+---------------+ 7168 1C00
| Reserved for | 6912 1B00
| Applications | 6656 1A00
| | 6400 1900
+---------------+ 6144 1800
| Reserved for |
| Applications |
| |
+---------------+ 5120 1400
| Reserved for |
| Applications |
+---------------+ 4864 1300
| Basic |
| Absolute |
| Variables |
+---------------+ 4608 1200
| Basic |
| DOS/VSP |
| Variables |
+---------------+ 4360 1108
| CP/M Reset |
| Code |
+---------------+ 4352 1100
| Function |
| Key |
| Buffer |
+---------------+ 4096 1000
| Sprite |
| Definition | 3840 0F00
| Area |
+---------------+ 3584 0E00
| RS-232 |
| Output |
| Buffer |
+---------------+ 3328 0D00
| RS-232 |
| Input |
| Buffer |
+---------------+ 3072 0C00
| Disk Boot Page|
|- - - - - - - -| 3008 0BC0
|Cassette Buffer|
+---------------+ 2816 0B00
| Monitor&Kernal|
| Absolute |
| Variables |
+---------------+ 2560 0A00
| Basic |
| Run-Time | 2304 0900
| Stack |
+---------------+ 2048 0800
| VIC |
| Text |
| Screen |
| (VM #1) |
+---------------+ 1024 0400
| Basic RAM Code|
|- - - - - - - -| 896 0380
| Kernal Tables |
|- - - - - - - -| 828 033C
| Indirects |
+---------------+ 764 02FC
|Kernal RAM Code|
|- - - - - - - -| 674 02A2
|Basic & Monitor|
| Input Buffer |
+---------------+ 512 0200
| System Stack |
|- - - - - - - -| 329 0149
|Basic DOS Using|
|- - - - - - - -| 272 0110
| F BUFFER |
+---------------+ 256 0100
| Kernal ZP |
|- - - - - - - -| 144 0090
| Basic ZP |
|- - - - - - - -| 2 0002
+---------------+ 0 0000
FIGURE 4-1, C128 computer memory map
4.3. BASIC EXAMPLES
Let's create a program that accesses the RAM expansion module.
1) Reset your computer in 40 column mode so the start-up message
is visible. The screen should display:
COMMODORE BASIC V7.0 122355 BYTES FREE
(C) 1985 COMMODORE ELECTRONICS, LTD.
(C) 1977 MICROSOFT CORP.
ALL RIGHTS RESERVED
2) Move the cursor up to the start-up message. Type some changes:
perhaps replace the number of bytes free, or put your name in
place of Commodore. Make all your changes with the cursor and
INST/DEL keys; be sure not to press (RETURN).
3) When you are satisfied with the changes, move the cursor to
the bottom line of the screen.
Type: STASH 1000,1024,0,0 (RETURN)
This command stores 1000 bytes from the computer's main
memory, beginning at address 1024 in the RAM expansion module.
Address 1024 marks the beginning of the text screen, the part
of memory where the current screen contents are stored.
4) PRESS: (SHIFT) and (CLR/HOME) to clear the screen. Type this
program:
10 FOR X = 1 TO 25
20 FETCH 1000,1024,0,0
30 SLEEP 1
40 PRINT"(SHIFT) and (CLR/HOME)"
50 PRINT X: SLEEP 1: NEXT X
5) Type RUN (RETURN). The altered startup message is fetched from
the RAM expansion module, displayed, then a counter flashes
and the image is fetched again.
This example gives you a starting point for more creative uses of
the RAM expansion. Let's try a simplified version of the graphic
demos included on the demonstration disk packed with your RAM
expansion module.
Turn the machine off and then on to clear the RAM expansion
module's memory. Note that using the reset button does NOT clear
the expansion RAM banks, only the C128 computer's main memory.
1) Clear the screen using (SHIFT) and (CLR/HOME).
2) Create a picture using graphic characters. Try a smiling face,
or other simple design.
3) Cursor down to the bottom of the screen.
TYPE: STASH 1000,1024,0,0 (RETURN)
4) When the computer responds READY, clear the screen.
TYPE: FETCH 1000,1024,0,0 (RETURN)
Your smiling face returns. Move the cursor up to the picture,
and alter it in some way. Perhaps change the smile to a frown,
or add eyebrows. Delete any unnecessary characters (such as a
READY message) by using the spacebar to go over them. Don't
use the (INST/DEL) key as this can change the arrangement of
your picture. Be careful to align the picture in the same
location it originally was. Use the spacebar to add lines of
space and move the picture up or down a row at a time if
necessary.
6) Move the cursor to the bottom of the screen.
TYPE: STASH 1000,1024,1000,0 (RETURN)
Notice that the starting address given for the RAM expansion
module is 1000, not 0 as in previous trials. This is because
we don't want to overwrite the existing screen with the
smiling face.
7) Clear the screen once again, and type this program:
10 FOR X = 1 TO 10
20 FETCH 1000,1024,0,0: REM SMILE FACE
30 SLEEP 1
40 FETCH 1000,1024,1000,0: REM FROWN FACE
50 SLEEP 1
60 NEXT X
8) Type (RUN) to view the program.
These examples make use of an area of RAM in the C128 computer
that is easy to access. Since the text screen always begins at
address 1024, and is exactly 1000 bytes long, we can safely
create as many text screens as we like. Each screen can be stored
in the RAM expansion module, in addresses 1000 bytes apart, and
later fetched without any problem.
Storing other types of data, such as programs, requires being
able to use machine language to view other addresses. Detailed
information about machine language and the machine language
monitor is contained in the C128 PERSONAL COMPUTER SYSTEM GUIDE.
5. TECHNICAL SPECIFICATIONS
It is possible to use the RAM expansion module in the ways
described in chapters 3 and 4 of this manual without being aware
of the RAM Expansion Controller (REC). The REC is the processor
inside the RAM expansion module that makes communication between
the C128 computer and the RAM expansion module possible. Both
CP/M and the built-in BASIC commands automatically control the
transfer of information. In order to gain more precise control
over the RAM expansion module, details about the REC are needed.
5.1. OPERATING MODES
The REC has four primary operating modes. These are:
1) Transfer a block of data from main memory to expansion memory
(BASIC command: STASH)
2) Transfer a block of data from expansion memory to main memory
(BASIC command: FETCH)
3) Exchange a block of main memory with a block of expansion
memory (BASIC command: SWAP)
4) Verify a block of main memory with a block of expansion memory
The REC has several internal registers which can be used to set
up a particular operating mode. Modes can be selected by setting
the appropriate bits in the command register (see Figure 5-1).
The starting C128 address, expansion RAM address, expansion RAM
bank, and number of bytes are all programmable values.
REC Register Description
+-------+-----+-------------------------------------------------------------+
|ADDRESS|BITS | FUNCTION |
+-------+-----+-------------------------------------------------------------+
| $00 | 7-0 | Status Register -- Read Only |
| | | 7 - Interrupt Pending; 1 = Interrupt waiting to be serviced |
| | | 6 - End of Block; 1 = Transfer complete |
| | | 5 - Fault; 1 = Block verify error |
| | | 4 - Size; 0 = Total expansion = 128K |
| | | 1 = Total expansion = 512K |
| | | 3-0 - Version; |
| | | Note: Bits 7-5 are cleared when this register is read |
+-------+-----+-------------------------------------------------------------+
| $01 | 7-0 | Command Register -- Read/Write |
| | | 7 - Execute; 1 = Transfer per current config. |
| | | 6 - Reserved; |
| | | 5 - Load; 1 = Enable AUTOLOAD option |
| | | 4 - FF00; 1 = Disable FF00 decode |
| | | 3 - Reserved; |
| | | 2 - Reserved; |
| | | 1,0 - Transfer type; 00 = transfer C128 --> RAM module |
| | | 01 = transfer C128 <-- RAM module |
| | | 10 = swap C128 <--> RAM module |
| | | 11 = verify C128 -- RAM module |
+-------+-----+-------------------------------------------------------------+
| $02 | 7-0 | C128 Base Address, LSB -- Read/Write |
| | | Lower 8 bits of base address, C128 |
+-------+-----+-------------------------------------------------------------+
| $03 | 7-0 | C128 Base Address, MSB -- Read/Write |
| | | Upper 8 bits of base address, C128 |
+-------+-----+-------------------------------------------------------------+
| $04 | 7-0 | Expansion RAM address, LSB -- Read/Write |
| | | Lower 8 bits of base address, expansion RAM |
+-------+-----+-------------------------------------------------------------+
| $05 | 7-0 | Expansion RAM address, MSB -- Read/Write |
| | | Upper 8 bits of base address, expansion RAM |
+-------+-----+-------------------------------------------------------------+
| $06 | 2-0 | Expansion RAM bank -- Read/Write |
| | | Expansion RAM bank pointer. |
| | | Bits 2 (MSB) to 0 (LSB) are significant |
+-------+-----+-------------------------------------------------------------+
| $07 | 7-0 | Transfer length, LSB -- Read/Write |
| | | Lower 8 bits of the byte counter |
+-------+-----+-------------------------------------------------------------+
| $08 | 7-0 | Transfer length, MSB -- Read/Write |
| | | Upper 8 bits of the byte counter |
+-------+-----+-------------------------------------------------------------+
| $09 | 7-5 | Interrupt mask register -- Read/Write |
| | | 7 - Interrupt enable 1 = Interrupts enabled |
| | | 6 - End of Block mask 1 = Interrupt on end of block |
| | | 5 - Verify error 1 = Interrupt on verify error |
+-------+-----+-------------------------------------------------------------+
| $0A | 7-6 | Address control register -- Read/Write |
| | | 0,0 = Increment both addresses (default) |
| | | 0,1 = Fix expansion address |
| | | 1,0 = Fix C128 address |
| | | 1,1 = Fix both addresses |
+-------+-----+-------------------------------------------------------------+
Figure 5-1
Note: The Base address of the REC registers in the C128 memory
map is DF00 in I/O space. The addresses of the REC registers can
be obtained by adding the value in the Address column in Figure
5-1 to the base address of DF00.
5.2. DIRECT MEMORY ACCESS OPERATION
Direct Memory Access (DMA) is the process the REC uses to
transfer data to and from the C128 computer's memory. During DMA
the C128 computer processor is temporarily halted so the REC may
access the C128 computer's memory.
There are two different events which cause the REC to begin a
transfer sequence.
1) If the FF00 option in the command register ($01) is disabled,
the DMA begins right after the execute bit is set in the
command register.
2) If the FF00 option in enabled, the DMA begins right after a
write to address FF00 is detected -- providing the execute bit
was set in the command register.
The purpose of the FF00 option is to allow the REC to access the
RAM beneath I/O space. The REC registers are I/O mapped on the
C128 expansion bus which means that, without the FF00 option, I/O
space would be enabled when the DMA was initiated. Address FF00
is the configuration register within the C128's MMU. This option,
therefore, allows the user to reconfigure the C128's memory
before the DMA takes place. The FF00 option is cleared each time
it is used.
5.3. SPECIAL FEATURES
AUTOLOAD -- One special feature is AUTOLOAD. Selecting this
option in the command register automatically reloads the C128
base address registers, the external memory base address
registers, the external memory bank, and the byte counter
registers at the end of the transfer.
This is useful if one operation is to be executed repeatedly on
one particular block of data. Note that in verify mode, if
AUTOLOAD is selected, the address where the verify error occurred
is lost. Ordinarily upon finding a verify error, the REC halts
the DMA cycle and both address registers and the bank register
point to one location above the address that failed.
ADDRESS CONTROL -- Another special feature of the REC is the
ability to hold a source and/or destination address fixed in any
mode. This is accomplished by setting the appropriate bits in the
address control register ($0A). The default is that addresses
will increment for both source and destination. It is possible,
with a fixed C128 address, to DMA to any C128 I/O device except
the 8563.
INTERRUPTS -- An interrupt can be generated on an end of block
condition or verify error by enabling interrupts and by setting
the corresponding mask bits in the interrupt mask register ($09).
In either case, the corresponding flag is set in the status
register. Interrupt flags are cleared upon reading the status
register. The interrupt mask register bits stay as they were
before the interrupt/clear sequence. For proper operation, the
status register ($00) must be read at least once before a DMA is
initiated with interrupts enabled. It is important to clear out
the previous status before any mode is used with interrupt
option.
5.4. OPERATION DESCRIPTION
If a specified address range exceeds the address range in the
selected expansion RAM bank, a "wrap" will occur into the next
bank. This will happen whenever the given byte counter exceeds
the number of bytes left in the selected bank. If the selected
bank is equal to the maximum for a particular memory
configuration, then the wrap is to bank 0. This will give the
appearance of contiguous memory. The C128 side always wraps to
the beginning of the same bank.
Under normal operation (no AUTOLOAD, addresses increment), both
address registers will point to the next sequential memory
location outside the selected transfer range at the end of the
transfer. This is true for any mode and applies to both base
address pointers except one that is held fixed. The bank pointer
will also be updated if necessary at the end of the transfer.
Also note that under normal operation, the byte counter
decrements to the value 1. Care should be taken, therefore, to
check the transfer complete bit in the status register and not
rely on the byte counter value to indicate an end of transfer
condition. A byte counter of 0 results in a transfer of a full
64K bytes. Again, wrapping occurs in all modes of operation.
Important operating notes
1) The Z80 must not be in control when a DMA is requested.
2) The REC cannot reconfigure the MMU during a DMA cycle.
3) On the C128 the DMA bank is set by the VIC bank pointer in the
MMU, not the processor bank pointer.
4) The C128 computer must be in 1 MHz mode when a DMA is
requested.
5.5. TIMING
The effective transfer rate is 1 Mbyte/sec for uni-directional
transfers via STASH and FETCH, and 500 Kbytes/sec for
bi-directional transfers accomplished with SWAP. This transfer
rate does not include VIC DMA time. The VIC chip has highest
priority on the C128 computer unless it is disabled, so VIC DMA's
take precedence over REC DMA's.
5.6. BANK CONFIGURATION
Bank Select (BS) is provided as a means of configuring the
controller so it can direct RAS and CAS to the appropriate bank.
+------+----------------+----------------+------------+
| BS | Bank I | Bank II | Total |
+------+----------------+----------------+------------+
| 0 | 64K x 1 | 64K x 1 | 128K |
| 1 | 256K x 1 | 256K x 1 | 512K |
+------+----------------+----------------+------------+
This bit in the status register reflects the state of an external
jumper which was preinstalled in the factory.
5.6. NOTES FOR BASIC PROGRAMMERS
The BASIC commands STASH, FETCH, and SWAP can only be used to
transfer and retrieve data in Bank 0 of the C128 computer's
internal RAM. To access Bank 1 of the C128 computer it is
necessary to alter a special control register on the C128. This
register is the RAM control register in the MMU, address $D506.
Bits 6 and 7 of this register control both the VIC RAM bank
pointer and the C128 DMA bank pointer.
+---------+----------+----------------------+
| Address | Bits | Function |
+---------+----------+----------------------+
| $D506 | 6-7 | 00 C128 Bank 0 |
| | | 10 C128 Bank 1 |
+---------+----------+----------------------+
Be sure to restore these bits to their original values or your
40-column screen will contain the wrong information.
Note that I/O is enabled for the three BASIC commands in Version
0 of the C128 kernal ROM. In Version 1 of the ROM I/O can be
disabled by using the BANK command. See the C128 Personal
Computer System Guide for details on the BANK command.
The kernal ROM version can be determined by PEEKing location
$FF80. Version 0 contains a 0 while Version 1 contains a 1.
*********
End of Project 64 etext 1700/1750 RAM Expansion Module User's Guide.
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