LJ MAC III 6502 User manual

©LJ Technical Systems
This publication is copyright and no part
of it may be adapted or reproduced in
any material form except with the prior
written permission of LJ Technical Systems.
Issue Number: MP600/C
Written by: LJ Technical Publications Dept.
LJ Technical Systems Ltd.
Francis Way
Bowthorpe Industrial Estate
Norwich. NR5 9JA. England
Telephone: [phone]
Fax: [phone]
LJ Technical Systems Inc.
85, Corporate Drive, Holtsville,
11742-2007, New York, USA.
Telephone: [phone]
Fax: [phone]
LJ Technical Systems
MAC III 6502 Microcomputer
User Manual
MP600/C

MAC III 6502 Microcomputer
User Manual Contents
LJ Technical Systems
Chapter Contents Pages
Introduction ..................................................................................................... 1 - 2
Chapter 1 Hardware Description ................................................................. 3 - 4
Chapter 2 Digiac 2000 Connections ............................................................ 5 - 8
Chapter 3 Digiac 3000 Connections ...........................................................9 - 12
Chapter 4 Monitor Functions ................................................................... 13 - 22
Chapter 5 Memory Map ........................................................................... 23 - 24
Appendix 1 Applications Module Programs ...............................................25 - 30

MAC III 6502 Microcomputer
Contents User Manual
LJ Technical Systems

MAC III 6502 Microcomputer
User Manual Introduction
Introduction
LJ Technical Systems 1
The MAC III 6502 is a complete, working microcomputer system based around the Rockwell 6502
microprocessor.
A keypad/display unit may be connected to provide simple memory edit/display and debug
functions, plus direct entry of short programs written in machine code.
For more advanced program development work, the MAC III board may be used in conjunction
with the Merlin Development System, to allow students to design, develop and download programs
written in assembly language using a personal computer (PC).
An optional Applications Module may be connected to the MAC III board. This provides a number
of devices that may be controlled by programs written by the student.
Chapter 1 of this User Manual provides a hardware description for each of the main features of the
MAC III board.
The MAC III board may be connected in one of two ways: in a Digiac 2000 system, or as part of a
Digiac 3000 system. Chapter 2 and Chapter 3 explain how to connect the MAC III board and
related hardware when using these systems. You should refer to the appropriate chapter for the
system you are using.
Chapter 4 provides an overview of the software features of the MAC III board, while Chapter 5
details the programming memory map that will be essential when writing programs to run on the
MAC III.
Finally, Appendix 1 explains how to control the Applications Module using the programs provided
in EPROM on the MAC III board.
The following teaching manual provides further, detailed instruction on developing applications
programs for the MAC III board:
A Introduction to 6502 Microprocessor Applications

MAC III 6502 Microcomputer
Introduction User Manual
2 LJ Technical Systems

MAC III 6502 Microcomputer Hardware Description
User Manual Chapter 1
Chapter 1
Hardware Description
LJ Technical Systems 3
This chapter provides a hardware description of the main features of the MAC III board. A
functional block diagram is shown on the following page.
Microprocessor The MAC III system uses a Rockwell 6502 microprocessor operating at a
clock frequency of 1 MHz.
Monitor EPROM Memory space for 16 kbytes of EPROM is provided. This can be fitted with a
27128 16k EPROM or a 27256 32k EPROM (in this case only half of the
device is used). This EPROM contains the monitor software.
User EPROM A socket is provided for an 8kbyte 2764 type EPROM which can be used for
application programs.
RAM An 8kbyte 6264 type RAM is fitted to the board. This provides 7kbytes of
memory for user programs, the remainder being used for system variables.
User Input/Output A 6522 VIA provides 16 TTL-compatible user input/output lines for
controlling external devices.
Counter/Timer The 6522 also provides two programmable counter/timer channels.
RS-232 Interface A 2681 DUART provides two independent RS232 channels for serial
communication with other devices.
Switched Faults Eight on-board fault switches are provided under a lockable cover. These
allow faults to be switched into the system for fault-finding exercises.

Hardware Description MAC III 6502 Microcomputer
Chapter 1 User Manual
4 LJ Technical Systems
F
unctional Block Diagram for the MAC III board

MAC III 6502 Microcomputer Digiac 2000 Connections
User Manual Chapter 2
Chapter 2
Digiac 2000 Connections
LJ Technical Systems 5
When used as part of a Digiac 2000 system, the MAC III Microcomputer board is powered from a
DT60 Power Supply unit. A DT25 Keypad/display unit may be connected to the MAC III to allow
simple display/editing of memory locations and machine code programming, and the optional DT35
Applications Module provides a range of devices that may be controlled by user programs.
The following picture shows a Digiac 2000 system:
Full instructions for connecting the MAC III Microcomputer board in a Digiac 2000 system, are
provided on the following page.
DT35
Applications
Module DT25
Keypad/display
unit
DT60
Power supply
Microcomputer
board

Digiac 2000 Connections MAC III 6502 Microcomputer
Chapter 2 User Manual
6 LJ Technical Systems
Connecting Power and Keypad/display to the MAC III board
Ensure that the power supply is switched OFF.
Connect the DT60 Power Supply to the MAC III board as shown below.
Note that the power supply cable with the ‘barrel’ connector is used for this
purpose.
Connect the Keypad/display Unit to the MAC III Microcomputer Board as
shown in the diagram.