Cromemco Z80 Instruction Manual

--

-

'J- _

InstructIon Manual

[3Cromemeo

i n cor p 0 rat e d

Specialists in computers and peripherals

2400 CHARLESTON RD., MOUNTAIN VIEW, CA 94043

© Copyright 1977. All rights reserved.

C3Cromemeo

incorporated

Specialists in computers and peripherals

2400 CHARLESTON RD., MOUNTAIN VIEW, CA 94043

Table of Contents

Pg.No.

Introduction 1
Entry 1

System Stack 1
Command Format 1

Swath Operator 1
Multiple Commands: The After Operator 1

Example 1: Writing Paper Tapes
Example 2: Copying Paper Tapes
Example 3: Multiple Copies of PROMs
Example 4: Initializing UARTs

Example 5: A Timer
Errors and Escapes 3
Input and Output 3

Baud Rates and UART Selection 3
Interrupts 3
Loading the Monitor .4
Using the Monitor .4

COMMANDS 4

Display Memory, DM

Display Registers, DR

Go,G

Go with Breakpoints Set, G/

Initialize Baud Rate, I

Move, M
Nulls, N
Output, 0
Program PROMs, P
Read, R
Substitute Memory, 8M

Substitute Register

SA, SB, SC, SD, SE, SF, SH,
SI, SN, SP, SS, SX, SY,
SA', SB', SC', SD', SE', SF', SH'

UART Select, U
Verify, V
Write, W

Program Listing 7
Cross Reference 24

Z80 Monitor

~ Introduction

The Z80 Monitor makes it possible to control
computers which use the CROMEMCO zputm from a
terminal keyboard. It includes executive commands to

examine and change memory, make a binary or an
ASCII dump of memory, move and compare blocks
of memory, output a byte of data to any port, read,
write, and punch nulls on binary paper tapes, program
2708 and 2704 PROMs using the CROMEMCO BYTE-
SAVER, and initialize and control both serial ports on

the CROMEMCOTUART.

Transfer of control to a program in memory can
be commanded from the keyboard with up to five

breakpoints set and with the initial contents of the
ZPU registers specified. When a breakpoint is en-
countered during execution, control is transferred

back to the monitor and the contents of all 22 ZPU

registers are stored. These register values can be exam-
ined and changed before execution of the program

is resumed.

Entry Points

The Z80 Monitor has three entry points. A

cold-start entry at EOOO hex selects bank 0 on

CROMEMCO memory boards and UART A on the

'-------"CROMEMCO TUART. It initializes the baud rate of

the UART to match that of the terminal being used. In
addition, it saves the contents of the Z80 registers I,

N (IFF), S (SP) , X (IX) , Y (IY) , A' , B' , C' , D' , E' ,

F' , and H' (HL') in the user-register area which is part
of the system stack. (If the Z80 stack pointer is point-

ing to RAM, then all registers except A and P (PC) will
be saved.) The contents of these registers are restored
when the monitor is exited by means of the GO

command.

The warm-start entry point at E008 hex is pro-

vided so that the monitor can be re-entered without
affecting the memory banks or the UART. The same
registers are saved as for the cold-start entry point.

The third entry point is used by the break-

point facility. Entry here saves the contents of all
registers. Memory banks and UART are unaffected.

System Stack

The monitor does not require the user to
address a RAM board at a special place in memory for
its stack and working storage area. (However, if the
breakpoint facility is used, there must be either RAM
at locations 30, 31, and 32 hex or PROM with the data

C3, 45, EO hex at those locations.) The monitor finds

the highest page of RAM active in the machine and

places its stack and temporary storage area there. At
least 60H or 96 bytes of this page must be reserved for
system use. If the multiple command facility is used,

1

-------- ---- --

- - ------ ---

= -- -===-=- ~=

- ----~ --.•.. ""-""" ~

each additional command in a command line requires
an additional 20 hex or 32 bytes stack room. (See

Multiple Commands.)

Command Format

The Z80 Monitor is controlled by one and two-
character commands from the terminal keyboard. The
format is free-form with respect to spaces.

In the following, DM is the Display Memory com-
mand and S is the Swath operator (see below). The
four examples are equivalent commands. They display
the contents of 100 hex bytes of memory beginning
with location 1000 hex. (' (CR) , indicates a carriage

return.)

DM1000 10FF (CR)
DM1000S100 (CR)

D M 1000 10FF (CR)
D M 1000 S 100 (CR)

When entering an address as a operand, only the
last four digits typed in are retained. For example,
'321000' is read as '1000'. Therefore, if a wrong digit
is entered, continue typing until the last four digits are

correct.

Only the last two digits typed are retained when a

two-digit number such as a data byte is entered.

Swatl. Operator

There are two ways to specify the address
range of many commands. The first is to simply list
the beginning and ending addresses (and, where
appropriate, the destination address). For example, the
first command below programs the range 0 through

13FF into PROMs starting at E400. The second com-

mand displays the contents of memory between
addresses E400 and E402.

PO 13F F E400
DME400 E402

Another way to do the same thing is to use the
Swath operator, S, to specify the width of the address

range rather than state the ending address explicitly.

PO S1400 E400
DM E400S3

Multiple Commands:

The After Operator

The After operator, , < " can be used to place

more than one command on a command line. All of

Z80 M -~ --- --- - ----=--=-

ODIlOr 5.-= =-- === .: -=

-==.:::..::::.-.=..:.=.::..===.;::.::..:::._-------------

the commands on the command line are executed
before the monitor returns with its prompt' : " for

a new command.

With this feature, the monitor can write an area
of memory onto paper tape preceded and followed by
a sequence of nulls without any undesirable carriage-
returns or prompts inserted by the monitor.

Example 1

where, again, all colons are provided by the monitor. ~
Example 3

Suppose we wish to make three copies of the

same PROM. Assume that the source is in RAM at
location 0 and that we want three identical copies in
PROMs located at E400, E800, and ECOOhex. The

following command line will accomplish this:

Example 4

:POS400 ECOO<:POS400 E800 <:POS400 E400 (CR)

First, we re-initialize the UART by typing the

following:

:1 < :VB (CR)

:VA<:I < :VB (CR)

Time (minutes)

0.035

3.5

7.0

14.0

28.0

56.0

112.0

Number of
Bytes (hex)

10

640

C80

1900
3200
6400

C800

After entering one of these commands on the
console connected to UART A, push CARRIAGE-
RETURN on the other terminal until the monitor

prompt' : ' appears.

Either of the following will initialize the baud

rate of a terminal connected to UART B of the
TUART:

Example 5

Assume that we would like to take a brief nap to ~

refresh ourselves but have no alarm clock. Assume
further that two beeps of the console bell spaced 2.1

seconds apart are sufficient to wake us and that the
console can run at 300 baud. Since the Display Mem-
ory command takes 63 characters to display 10 hex or

16 bytes of memory, at 300 baud it takes 2.1 seconds

or 0.035 minutes to display 10 hex bytes.

Example 2

Assume that we are using a CROMEMCO TUART
I/O card with a console connected to UART A and
with a paper tape reader and punch connected to the
input and output, respectively, of UART B. Assume
that the baud rate of UART B has already been set to
that of the reader and punch. (See Baud Rates pg. 3.)
We can copy a paper tape by switching the current
UART to B, reading the tape into a memory buffer,
writing a leader, writing the buffer to the punch, and
finally switching the current UART back to A, the

console, by typing:

Assume that the terminal being used is a teletype-

writer with paper tape punch. In order to write the
contents of 400 hex bytes starting at 100 hex with a
leader of 95 hex nulls and a trailer of 80 nulls, type:

:N80 < :W100 S 400 <:N 95 (CR)

:VA < :WOS2000 < :N80 < :ROS2000 < :VB (CR)

where the colons are prompts provided by the monitor.
Turn on the paper tape punch after typing the carriage-
return in order to avoid writing it onto the tape.

There are several points to be made about the use

of the After operator:

(a) The order of execution of the commands is
from right to left. Hence, the name 'After' and the
shape'

< '.

(b) The After operator is logically equivalent to a
carriage-return. Anywhere a carriage-return can reason-
ably appear in a command, the After operator may be
used instead. However, no commands in the line are
executed until an actual carriage-return is typed.

(c) If any of the GO commands appears in a
multiple-command line, it must be the last command
executed, i.e., the first command typed.

(d) Each additional command on a line adds from
10 to 20 hex bytes to the system stack size.

In this case, we can leave the reader and punch on
all the time. There is no question of a carriage-return
from the command line being punched onto the paper
tape since two different UARTs are involved.

Perhaps we forgot to write nulls as a trailer to the
output tape. After the prompt, , : " again appears on
the console, we can rectify this by typing:

:1(CR)

Set the console baud rate to 300 and push the

CARRIAGE-RETURN until the monitor issues its
prompt,': '. ~

To ring the bell, output 7 to port 1. For a nap of

14 minutes:

:V A < :N 80 < : V B (CR)

:0 7 1 < :DMOS10 < :07 1 < :DMOS1900 (CR)

2

Z80 M -., --------- ----~-=-

onIlor = -_ -=--==;;=== _~~

-=:=.;:;...;:;;......=.:.=-=~~.;;;;.,;,~--------------

Errors and Escapes

When the monitor detects an error condition, the

command is aborted, all breakpoints are cleared, and a

'?' is printed followed by the prompt ' : ' for the

next command.

Any command may be aborted from the keyboard

either when the monitor is requesting further input, or
during print-out, by depressing either the ESCAPE or

the ALT MODE key. CONTROL-SEMI-COLON,
CONTROL-SHIFT-'K', and' }' may also work.

The baud rate can also be changed by using the

Initialize command (see page 5).

Some peripheral devices such as paper tape read-
ers or punches may have no keyboards. The TUART
baud rate can also be set by outputting a data byte
from the following table to port 0 for the currently
selected UART or to port 50 hex for the unselected
UART. (To make UART B current, output 80 hex to
port 4. For UART A, output 0 to port 54 hex. UART
selection can also be accomplished by means of the
monitor's UART command, U).

Interrupts

The baud rate can be octupled by outputting 10
hex to port 2 for the selected UART or to port 52
hex for the other UART. Outputting 0 to these ports
brings the baud rate back to normal.

The monitor can be used to enable interrupts in

the Z80. This is done by changing the value of the N

register to 1 by using the Substitute Register com-

mand, SN. (The N register stores the value of the Z80
interrupt flip-flop at the time the monitor is entered.)
Then interrupts will be enabled when one of the Go
commands is given.

Note, however, that the interrupt mask registers

on the TUART must have been set previously, either
by a user program or by the monitor. (If this is not

done, then an immediate interrupt will be generated

because the print buffer is empty.) To mask out all
interrupts output 0 to port 3 for the current UART

and to port 53 hex for the other UART.

The mask bit corresponding to each of the pos-
sible interrupts is given in the following table:

Input and output

The monitor assumes that a data transfer occurs

on I/O port 1. Status flags are transmitted over input

port O. The data-available flag is on bit 6 of input port

O. The transmitter-buffer-empty flag is on bit 7 of
input port O.Both flags are active high.

To use the CROMEMCO TUART with the

monitor, set switches 1, 7, and 9 of the 10-position
TUART switch OFF, all others ON. The currently

selected UART uses I/O port 1 for date transfer and
input port 0 for status flags. The UART which is not
current uses I/O port 51 hex for date transfer and
input port 50 hex for status flags. (The UARTs are
selected by means of the UART command.)

The following locations may be changed for dif-

ferent I/O conventions:

Status port number (00): EOOF, E020
Input data port number (01): E014
Output data port number (01): E027
Input-data-available mask (40): E011
Output-transmitter-buffer-empty mask (80): E022

For active-low status flags change locations E019

and E379 from 28 hex to 20 hex and change location
E120 from 20 hex to 28 hex.

Baud Rates
and UART selection

Baud Rate

110
150

300
1200
2400

4800

9600

Data Byte

01

82

84

88
90

AO

CO

When the monitor is entered at EOOOhex, the

cold-start entry point, push CARRIAGE-RETURN
until the monitor responds with:

CROMEMCO ZM1.4

The monitor is capable of selecting 19200, 9600,
4800, 2400, 1200, 300, 150, or 110 baud when used
with the CROMEMCO TUART I/O board.

The maximum number of carriage-returns re-
quired to select any of these baud rates is four. (Two
carriage-returns are required for any UART with a
fixed baud rate.)

3

Bit Interrupting Device

o Timer 1
1 Timer 2
2 Sens (external)
3 Timer 3
4 Receiver Data Available

5 Transmitter Buffer Empty
6 Timer 4

7 Timer 5 or external

For example, to allow only interrupts from the serial
input port and from Timer 1 on the current UART,
output 11 hex to port 3 and 0 to port 53 hex.

Z80M -. --------------=

-=.:~..::.:.::.o::..:;n~I;;;;.;:;..lo..;;..;:r~ =_- ' ....::_

Loading the Monitor

The paper tape can be loaded into RAM and

thence into PROM as follows.

Temporarily address a RAM card at EOOO hex.
Address the BYTESA VER card at some other address,
say AOOOhex. Place an erased 2708 in PROM position 1
(A400 hex).

Enter the following loader program via the front
panel switches at any convenient address. Since' it

only contains relative jumps, it will execute anywhere
in memory without change. The places that may need
to be altered for different I/O conventions are under,

lined.

CARRIAGE-RETURN twice. The monitor will then ~
respond:

CROMEMCO ZM1.4

followed by a prompt' : '. The monitor is then ready
to accept commands from the keyboard.

COMMANDS

DISPLA Y MEMORY

[1] DM beginning-addr ending-addr (CR)

P EOOO S 400 A400 (CR)

Align the first byte of data on the paper tape over

the read sensors of the paper tape reader. Begin execu-
tion of the loader program and then turn on the reader.
After the tape is read, stop the reader.

If necessary, change the monitor locations indi-

cated above to fit your I/O conventions.

Execute the monitor starting at location EOOO

hex. Depress carriage return several times to set the

baud rate to suit your terminaL The monitor will now

program itself into the PROM at A400. Turn on the
BYTESA VER program power switch and enter the

following command:

21 00 EO

DB 00
E6 40

28 FA

DB 01

77

23

18 F4

LD HL, OEOOOH

LOOP: IN A, (STATUS)

AND DAV
JR Z, LOOP

IN A, (DATA)
LD (HL), A

INC HL
JR LOOP

or
DM beginning-addr S swath-width (CR)

The contents of memory are displayed in hexa-
decimal form. Each line of the display is preceded by
the address of its first byte. Example:

:DMI00 S3
0100: C3 34 7F

DISPLAY REGISTERS

[2] DR (CR) ~

When the monitor is re-entered from a breakpoint,

the contents of all the Z80 registers are stored in an

area called the user-register area. (When the monitor is
entered via reset or the warm-start entry point, all
registers except A, B, C, D, E, F, HL, and P are saved
in the user-register area. However, if the stack pointer
is pointing to RAM, then all but A and P will be saved.)

DR causes these stored registers to be displayed

in the following format:

If the PROM programs correctly, the monitor will
respond with a line feed and the prompt' : '. Turn off
the program power switch and the computer power

switch. Re-address the BYTESA VER to EOOO and
move the monitor PROM to PROM location O. Change
the RAM address to something other than EOOO. You
are then ready to use the monitor in PROM.

using the Monitor

Set the power-on jump switch on the Cromemco
ZPU card to E (1110 binary). Whenever the computer is
reset, control will then immediately pass to the monitor.

If the ZPU is used with the Cromemco TUART
I/O card, depress CARRIAGE-RETURN two to four

times. This will set the UART on the serial interface
card to the baud rate of the terminal being used.

When used with a serial interface card with baud
rate fixed to that of the terminal, simply depress

4

A=OI B=12 C=34 D=56 E=78 F=9A HL=BCDE

I=FO N=OO P= 1234 S=5678 X=9ABC Y=DEFO

A'23 B'45 C'67 D'89 E'AB F'CD HL'EFOI

If interrupts were enabled when the monitor was
entered, then N=1. Otherwise, N=O.

The flag registers, F and F', are packed as follows:

S,Z,x,H x,P/V,N,C

i.e., sign, zero, (unknown), half-carry, (unknown),
parity or overflow, subtraction, and carry flags.

GO

[3] G (CR) ~

The Z80 registers are loaded with the values saved
in the user-register area. (These are the values displayed
with the DR command.) Execution then resumes at

Z80 M _I -------------=--=--

OnIor == -=-===:=::~====-::==

'=='= ~ =:s--=- :::: ~~-=-

-==.;:~~.;;;.;",;;;;.;:~;;;....;....;;,---------------

the location contained in the user-pro gram-counter, P.

~ .

[4] G startmg-addr (CR)

This command is exactly like [3] except that the
user-program-counter, P, is first loaded with starting-
address. Thus, execution begins at starting-address.

GO WITH BREAKPOINTS SET

[5] G / breakpoint-addr-1 breakpoint-addr-2 ... (CR)
[6] G starting-addr / brkpt-addr-1 brkpt-addr-2 ... (CR)

Commands [5] and ] 6] are like [3] and [4],
respectively, except that breakpoints are set at
breakpoint-address-1, breakpoint-address-2, etc.

When a breakpoint is encountered in the execu-
tion of the user program, the monitor is re-entered. All
registers are saved in the user register area (which is
part of the system stack), the address of the breakpoint
is printed, and all breakpoints are cleared (i.e., the user
program is restored to its original state). Finally, the
prompt, , : ' is issued for the next command from the
keyboard. Note the following about the use of break-
points:

(a) Breakpoints can only be set in programs resid-
ing in RAM. This is because the monitor inserts a RST
48 instruction (F7 hex) at each breakpoint location.
(The original contents of these locations are saved so
that they can later be restored.)

(b) Up to five breakpoints can be set. If an
attempt is made to set a sixth breakpoint, the monitor
will print a question mark to indicate error, erase all
breakpoints, and prompt for a new command.

(c) When a breakpoint is set, the monitor inserts
a 3-byte jump instruction at location 30 hex. This
means that locations 30, 31, and 32 hex are not avail-
able to the user program when breakpoints are used.

(d) The monitor temporarily uses ten bytes on
the user's stack in executing a breakpoint. The area
reserved for the user's stack must, therefore, be at least
ten bytes larger than that required for the user's
program.

(e) If breakpoints are set in a program and the
computer is reset and the monitor re-entered before
any breakpoint is reached in the execution of the pro-
gram, then the breakpoints will have to be removed
from the program by means of the Substitute Memory
command, SM. However, if any breakpoint is reached,
all breakpoints are automatically cleared by the

monitor.

INITIALIZE BAUD RATE

[7] I (CR)

After the CARRIAGE-RETURN is typed, change

the baud rate of the terminal to the desired value and

then push the CARRIAGE-RETURN until the monitor
responds with its prompt, , : '.

5

The monitor is capable of selecting 19200, 9600,
4800, 2400, 1200, 300, 150, or 110 baud when used
with the Cromemco TUART I/O board. The maximum
number of carriage-returns required to select any of

these baud rates is four.

The command is particularly useful for setting
the baud rate of the second serial port on the TUART.
(See Multiple Commands.)

MOVE

[8] M source-addr source-end destination-addr (CR)

or

M source-addr S swath-widthdestination-addr (CR)

Move the contents of memory beginning with
source-address and ending with source-end to destina-
tion-address. After the move, the monitor verifies that

source and destination are the same. This will result in
a print-out of discrepancies which are not really errors

after certain types of overlapping moves. However, this
print-out can be terminated by depressing ESCAPE
or ALT MODE.

The Move command can be used to fill a block of
memory with a constant. For example, to enter zeros
between locations 100 and 108, use the Substitute

Memory command to enter 0 at location 100, and then
move 100 through 107 to 101:

M100 107 101

or

M 100 S 8 101

Care should be taken not to overwrite the system
stack which resides in the top of active RAM. (See
System Stack.)

NULLS

[9] N hex-number (CR)

Write hex-number nulls to the current device.
This command is used to punch leaders and trailers on
paper tape. (See Multiple Commands.)

OUTPUT

[10]

0 data-byte port-number (CR)

Outputs data to a port. One use of this command
is to select banks on Cromemco memory boards.
When the monitor is first entered on power-up or reset,
it selects bank 0 and turns off all other memory banks.

Either a software output or a monitor output to
port 40 hex serves to change the bank selection. To
select bank n, output a byte with bit n high. To select
two banks, nand m, output a byte with both bits n

and m high.

Z80 M _I ------------~~

Onl or == --=======~====:'==

~ = -=.:- =~S"-=- ==::-~~

....:;=-.;;...;;......:;;"";,,,;;~...;;;;;;.;;;;.;......;;;..~----------------

Bank

o

1

2
3

4

5

6

7

Output byte

01

02

04

08

10

20
40

80

Read binary or ASCII input from paper tape
reader or console and store in memory from destination-
address through destination-end. After destination-end

has been filled, the monitor prompts for the next

command.
SUBSTITUTE MEMORY

[13] SM address (CR)

For example, the first command selects bank 5 and the
second selects banks 4 and 5.

o

20 40

o 30 40

PROGRAM

[11] P source-addr source-end destination-addr (CR)

or

P source-addr S swath-widthdestination-addr (CR)
Program from source-address through source-end

into PROMS beginning at destination-address.

If the length of the source is not a multiple of
400H (1024 decimal) or if the destination does not
begin at 400H boundary, the monitor will reject the
command. (Multiples of 400H end in '000', '400',

'800', or

'COO'.)

Any number of 2708 or 2704 PROMS can be

programmed in the execution of one command as long
as there are enough BYTESAVERS to contain them.
Each PROM is verified with its source after all are pro-

grammed and any discrepancies are printed out. If
there are none, the prompt ' ; , is issued and the
monitor awaits the next command.

Software can be loaded into a PROM in as small
increments as you desire provided it is added to pre-

viously unused areas of the PROM.

This is done by first using the Move command,
M, to transfer the current contents of the PROM down

to RAM, adding the new software to an area of RAM

which corresponds to the unused portion of the PROM

and finally using the Program command, P, to re-

program the PROM with the result.

Although the entire PROM must always be pro-

grammed, it never hurts to re-write the same data
over again.

In general, a 1 may be written over a 1, a 0 over

either a 1 or a 0, but the only way to change O'sto l's
is to erase the PROM with appropriate UV light. (See
the BYTESAVER manual for details.)

READ

[12] R destination-addr destination-end (CR)

or

R destination-addr S swath-width (CR)

6

Substitute Memory desplays the contents of
address and outputs a dot,' . ',as a prompt for the
substituted value. If no change is desired, type a
space or another dot. Otherwise, enter the new value.

The monitor accepts hex digits until it gets a delimiter,
such as a space, dot, or carriage-return retaining the
last two digits entered as the value. Unless the delimiter
is a carriage-return, the monitor outputs the contents
of the next sequential memory location with a dot
prompt. A carriage-return terminates the command.

SUBSTITUTE REGISTER

[14] S register-name (CR)

Register-name may be A, B, C, D, E, F, H (HL), I,
N (state of the Z80 interrupt flip-flop), P (PC), S (SP),
A', B',

C', D', E', F', H' (HL'), X (IX), or Y (IY).

This command prints the name of the user-register
requested, displays its contents, outputs a dot,' . ',as

a prompt for the substituted value. If no change is
desired, type a space or another dot. Otherwise, enter
the new value. The monitor accepts hex digits until it
gets a delimiter such as space, dot, or carriage-return
retaining the last two digits (four digits for a 2-byte
register). Unless the delimiter is a carriage-return, the
monitor prints the name and contents of the next
register followed by the dot prompt. A carriage return

terminates the command.

UART SELECT

[15] U device-name (CR)

Device-name may be A or B. The Cromemco
TUART has two UARTs. When the monitor is entered

via reset, UART A is selected for its input/output
channel. This command allows the user to change the

UART selection. It is often used in the multiple com-

mand mode (see page 2).

VERIFY

[16] V source-addr source-end destination-addr (CR)

or
V source-addr S swath-width destination-addr (CR)