RCA COSMAC User manual

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LSI Systems Design
2nd Draft, February 1975
Copyright 1974, 1975 RCA ~orporation
Operator's
Manual
Solid State Technology Centel
Somerville, N. J

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nell
LSI Systems Design
2nd Draft, February 1975
Copyright 1974, 1975 RCA Corporation
I
Operator's .
Manual
Solid State Technology Center
Somerville, N. J.

TABLE OF CONTEllTS
PAGE
INTRODUCTION
OPERATING AND PROGRAMMING THE MICROKIT
System Overview and Initial Operation...... 2
Instruction Set and Memory Organization........ 6
COSMAC Instruction Set................... 6
Memory
Organization...................... 6
Introduction to Utility Package - UT2.......... 8
Machine Language Programming .••••..•..•••••••.• 13
Programming Interface to CSDP ••••••••.••••••••• 18
UT2 Features and Calling Sequences •••.•••.••••• 26
UT2 Read and Type Routines ••••••.••••••.• 26
UT2 Register Storage Option .•••.•••••••.• 31
MICROKIT HARDWARE STRUCTURE AND INTERFACING
System Block Diagram •••••••••.••••....•••••••.• 32
Module Descriptions •....• · ••••.••••.•...••...••• 34
CPU Module............................... 34
Clock and Control Module ••.••••..•.•...•• 35
Address Latch Module •••••••••.•.•••.•••.. 37
5l2-Byte RAM Module ••..•••••..••.••••••.. 38
5l2-Byte PROM Module •••.••••.••••••.••••• 39
I/O Decoder Module ••••••••••••••••••• ~ ••• 40
Bus
Separator Module •••••••••••••••.••••• 41
Byte I/O Module •.•••••••••••.•••••••••••. 42
Terminal Module •.•••••••••••••••••••••••• 43
Card Nest and Signal-Naming Conventions .••••••• 44
Memory Module Addressing Details ••••••••••••••• 47
RCA ~1odules.............................. 47
Example A........................... 47
Example B........................... 48
Custom Memory Modules ••••••••••.••.•••••• 49
Input/Output Interfaces........................ Sl
Introduction............................. 51
The Module-Enable Philosophy and
Two-Level I/O ••••••••••••••••••••••• Sl
Interfacing Signals ••••••••••••.••••••••• 53
DMA. Input................................ S5
DMA. Output............................... S6
Interrupt. ............................... 56
Interfacing Examples..................... 57
Sample Program System •••••••••.•••.• 57
Bit Serial Interface -The Terminal
Module.......... .60
Interfacing Techniques and Precautions ••• 61
To Use External Clocks •••••••••••••• 61
External Flags EFI to EF4 ••••••••••• 61
Remote
Start/Stop •••••••••••••••••.. 62
Bus
Deseparator ••••••••••••••••••••• 62
Microkit Dynamic Characteristics •••. 62
Troubleshooting •• ,8 •••• ,.8.~., •. ~.~. 63
Hardware i Specifications ••••••••••••••• 1······· .. 64
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TABLE OF CONTErnS (cDtn'n)
PAGE
APPENDICES
A. TELETYPE HALF-TO-FULL DUPLEX CONVERSION
INSTRUCTIONS .••.• 66
B. UTZ ASSEMBLY LISTING •••••.•...•••••••.••.••..•.. 69
C. TTY -MODEM-MICROKIT SWITCHBOX .•••.••••••••••..••• 77
D. BACKPLANE WIRING SCHEDULE .•••.•••••••••••.•.•••. 79
E. MODULE LOGIC AND CIRCUIT DIAGRAMS ..•••••..••••.. 80-97
F. COSMAC INSTRUCTION SUMMARy .••••.••••••.••.•..... 98
G. ASCII - HEX TABLE •...•••.••...•.........•.....•. 99

TAB LEO F
FIGURE
NUMBER TITLE
FIG U RES
PAGE
1 I/O Typewriter Cable Connection 4
2
Elementary Hexadecimal Program Example 15
3 Source Code for Sample Program 22
4, Assembly Listing for Sample Program 23
5
Microkit Block Diagram 33
6
Block Diagram - CPU Module 34
7
Block Diagram - Clock and Control Module36
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Block Diagram - Address Latch Module
Block Diagram - 5l2-Byte RAM Module
Block Diagram - 5l2-Byte PROM Module
Block Diagram - I/O Decoder Module
Block Diagram -Bus Separator Module
Block Diagram - Byte I/O Module
Block Diagram - Terminal Module
Custom 4K RAM Functional Diagram
DMA Input Example
DMA Output Example
Sample Program Interface
Sample Character Waveform
Model 33
Teletype Terminal Strip
Detailed Circuits for CPU - Terminal
Interface (Full Duplex Mode)
TTY-MODEM-KIT Switchbox
37
38
39
40
41
42
43
50
55
56
58
60
67
68
78

TAB LES
TABLE
NUMBER TITLE
PAGE
1
VT2
Register Initialization
29
2 VT2 Calling Sequences
30
3 Card Nest
Hodule Assingments
44
APPENDIX
D Backplane
Wiring Schedule 79
APPENDIX
F COSMAC Instruction
Summary 96
APPENDIX
GASCII -Hex
Table
97

I NT ROD UCT ION
The COS~~C Microkit and the COSMAC Software Development
Packages comprise an environment for the design of sys-
tems based ~n the COSMAC microprocessor. While the
Microkit may be viewed as a "stand-alone" machine, it
is specially structured to provide a testhed in which
hardware/software prototypes of systems containjng the
COSMAC microprocessor may he designed, built and tested.
The Microkit consists of a card nest with self-contained
power supply, an easy-to-use control panel and a basic
set of plug-in modules. It is packaged to promote easy
interfacing with external devices. These interfaces may
be custom-designed by the user, or for common peripheral
devices, they may be available from RCA as standard
optional modules.
The COSMAC Software Development Package, or CSDP, provides
a fundamental set of programming aids to facilitate the
coding and debugging of application programs. The. Microkit
includes means to transfer program material from the CSDP sys-
tem to the Microkit memory. There it can be executed by
the COS~~C microprocessor.
This manual is designed as a guide for the Microkit user.
It includes a detailed description of each of the avail-
able hardware modules as well as a complete explanation of
the functions available from utility programs, pre-written
into a programmable read-only memory (PROM), which is part
of the Microkit.
- I -

OPERATING AND PROGRAMMING THE MICROKIT
SYSTEM OVERVIEW AND INITIAL OPERATION
The nest for the Microkit consists of a set of printed
circuit board connectors with associated card guides
and a built-in power supply and control panel. The first
21 of the 34 available connector positions are assigned
to specific module* types. Many of their pins are pre-
wired using a printed circuit (PC) board backplane and a
small number of additional wire-wrapped connections.
(The latter were specifically made removable to permit
possible user modifications.) The last 13 of the con-
nectors are available for .any use.
Table 3 (p.44) contains a list defining to which module
each of the first 21 card positions is assigned. Eleven
of these positions are occupied with modules supplied in
the minimal Microkit, as indicated in the list. All
logic functions are implemented in COS/MOS. One card
contains the two-chip COSMAC microprocessor (the CPU --
"central processing unit"). Three memory cards are
included -- two 512-byte RAM's (random-access memories)
and one 512-byte PROM (programmable read-only memory)
containing the prewritten UTILITY PROGRAM, henceforth
called UT2. The crystal-controlled system clock and the
control-pinel interface reside on a card. Two cards are
used to provide appropriate data routing within the system.
An additional module is used for memory address latching.
Finally, three cards provide a fundamental I/O (input/out-
put) interface (including I/O device selection decoding,
a two-way byte-parallel I/O port and an I/O typewriter
serial interface). It should be emphasized that a spec-
ific, custom COSMAC controller need not require all of
these hardware facilities, if it is sufficiently simple.
Detailed descriptions of each of the available modules
appear elsewhere in this manual.
The supplied UT2 program includes a set of routines pro-
viding basic functions which virtually all users are ex-
pected to need. These include capabilities to load memory,
to read memory and to initiate program execution. Other
built-in services which are available from these routines
will be described later.
* We will use the terms "module", "card", or "board" inter-
changeably -- to represent a pluggable unit. It is in-
serted into the nest in a specified "slot" or "numbered
position". Each such slot has its own connector, mounted
in the nest.
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SYSTEM OVERVIEW AND INITIAL OPERATION (cont'd)
The control panel provides an extremely simple user inter-
face. Depressing RESET initializes the CPU. Depressing
RUN UTILITY transfers control to UTZ. Depressing RUN PROGRAM
transfers control to memory location I (assuming some prev-
iously-loaded user program begins there). The RUN indicator
is illuminated whenever the CPU is running. The LOAD switch
is used to initiate byte-parallel memory loading using the
COSMAC "load mode" (discussed further later). This feature
is not utilized in the minimal Microkit, since program load-
ing and initiation are accomplished via standard services
supplied by UTZ.
The I/O typewriter interface supplied in the minimal Microkit
is designed to connect directly either to a user-supplied
ASR33 Teletype* or to a user-supplied Execuport** terminal
(or its electrical equivalent). The system is designed to
adjust to a variety of typewriter speeds. It will also
accommodate either FULL DUPLEX or HALF DUPLEX terminal oper-
ation. (For the reader's information, Appendix A provides
instructions for converting a Teletype from half duplex to
full duplex operation.)
Two I/O typewriter cables are supplied with the Microkit --
one for a Teletype, the other for an Execuport. They are
labeled appropriately. To connect the terminal, select the
proper cable and plug its receptacle labeled "PI" into the
appropriate connector mounted directly on the accessible end
of the Terminal board, in card position 20 (see Figure 1
below). The two connectors on the Terminal board are labeled
properly. The connector on the other end of the cable plugs
into the terminal. For a Teletype, remove the typewriter
cover and plug the cable into connector position 2(32) in
the array of white plastic Molex connectors located in the
back of the Teletype unit. For an Execuport, plug the Cinch
connector on the cable into the "External Device" receptacle***
(the bottom one) available on the back of the typewriter.
Figure 1, below, should clarify these connections. Note
that the plastic tie-downs, supplied in the Microkit, may be
used for anchoring the I/O typewriter cable.
NOTE: Due to specific hardware characteristics of the r/o typewriters
discussed above and of the terminal board, the Execuport Terminal should
be operated only in Half Duplex and the Teletype only in Full Duplex.
* Registered trademark, Teletype Corporation.
~* Registered trademark, Computer Transceiver Systems, Inc.
*** Models 310 and up only.
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SYSTEM OVERVIEW AND INITIAL OPERATION (cont'd)
TERMINAL PLUG-IN
MODULE (~LOT .20)
MOUNTED 1/0
TYPEWRITER
CONNECTORS
WHITE PLASTIC
MOLEX
JACK
CABLE) ~
E +- rPil--L----__=___ P2
L..~ .LABELED ./
END TELETYPE- /
RECEPTACLE
END
COON(CT~
ACCESSIBLE
END
CINCH
CONNECTOR
Fig. 1: I/O Typewriter Cable Connection
(see text above)
WHITE PLASTIC
MOLEX JACK
INSIDE
TELETY~
IN POSITION -2
d (J21
-[t
'! EXTERNAL DEVICE·
CINCH RECEPTACLE
ON BACK OF
EXECUPORT
TERMINAL
Once the I/O typewriter has been properly connected
(with the Teletype operating in LINE mode, or the Execuport
in LOCAL mode) and Microkit power switched on (after the
supplied power cable has been installed), a simple test can
verify that the system is functioning properly. Depressing
RESET causes the RUN light to go off and the CPU to idle.
Following this by a depression of RUN UTILITY will cause
the RUN indicator to light. The system is now running,
with UT2 (the utility program) in control. This program
begins by reading the first keyboard input character to
define for itself the terminal character rate and whether
or not it should "echo" typed information to the typewriter
printer. If the terminal is operating in the FULL DUPLEX
mode, the user should begin by hitting the RETURN key on the
keyboard. For the HALF DUPLEX mode, he should hit the LINE
FEED key instead. The system will then respond with the
'*' prompt character. It now "knows" the essential charact-
eristics of the I/O typewriter. Reaching this simple stage
already verifies that most of the hardware is operating properly.
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