DICK SMITH

VZ-200

EDITOR ASSEMBLER

INTRODUCTION

This Instruction Manual is not meant to

be a training course in ASSEMBLER LANGUAGE

programming, it is meant only to explain the

commands invovied with this EDITOR

ASSEMBLER, although the APPENDICES do

provide some important information for

writing MACHINE LANGUAGE programs on the

VZ-200 computer.

THE TEXT EDITOR

There are 5 basic commands used for text

entry and display, they are INSERT, DELETE,

EDIT, LIST and FIND. These are invoked by

using the first letter of each command eg.

1, D, E, L and F.

There are 5 tape commands, TAPE SAVE,

TAPE LOAD, TAPE VERIFY, TAPE MERGE and TAPE

OBJECT. These are invoked by using the first

letter of each word eg. TS, TL, TV, TM and

TO.

As well as the above 10 commands there

are 4 special purpose commands, ASSEMBLE,

RUN PROGRAM, ORIGIN and SET PARAMETERS.

These are invoked by using just their first

letter. eg A, R, 0 and S.

INSERT COMMAND

This command is used to input source

lines. It has two formats :-

I<RETURN> - this will start to insert lines

directly after the line pointed to by the

CURRENT LINE POINTER, this will be the line

last listed, normally just above the COMMAND

LINE.

Innn<RETURN> - this will start to insert

lines directly after line nnn.

After entering your line press <RETURN>

to store your line in the SOURCE BUFFER. A

new line number will be printed and you may

type in a new line. Pressing <CTRL> +

<BREAK> will exit the INSERT MODE and return

you to the COMMAND MODE.

LINE FORMAT

Each line, with only 3 exceptions, must

conform to the following format. Each fine

may contain a LABEL, must contain an OPCODE

and depending on the OPCODE an OPERAND. No

COMMENT Is allowed. The 3 exceptions are

COMMENT LINES, COMMAND LINES and MESSAGE

LINES.

If ayou wish to place a LABEL on a line

then it must occupy the first 1 to 4 places

of the line, no preceeding spaces are

allowed. The first character must be

alphabetical while tt)e last 3 may be

alphanumeric, no special characters are

allowed (eg. I"#$%&).

At least one space must separate the

LABEL and the OPCODE (if no LABEL was used

the first character of the line must be a

space). The OPCODE must follow the same

rules as the LABEL as far as number and type

of characters. Of course the OPC)ODE must be

one of the 71 recognised OPCODES by this

ASSEMBLER if it Is to be accepted at

assembly time. A list of these 71 opcodes is

given in APPENDIX A.

If an OPERAND Is required then at least

one space must be between it and the OPCODE.

%o check Is (ione on the OPF-RPND but the

first space found after the commencement of

the OPERAND will be taken as the end of the

line.

If the LABEL or the OPCODE do not conform

to the I to 4, alphabetical / alphanunerical

format then a LINE FORMAT ERROR will be

given and you will be asked to re-enter the

line.

COMMENT LINE

Comments must be on a line by themselves

and the line must start with a semi-colon

eg 001 ;GREAT GAME

002 ;WRTTTER BY G.BLOGGS

003 ;LAST UPDATE 12/12/84

COMMAND LINES

Command lines are used to send special

commands to the assembler during assembly.

These lines must be on a line by themselves

and start with a colon (:). The commands

they set are described under ASSEMBLY

OPTIONS.

MESSAGE LINE@,

The DEFM opcode is not allowed. If this

opcode was used for defining message they

would be limited to 18 characters - the max.

length an operand can be (due to the single

line entry format of the editor). While this

is long enougth for any operand It does

limit messages. Of course messages longer

then 18 characters could be defined with 2

DEFM opcodes and it would be the same thing

as far as the finished assembly would be

concerned. But to make message handling a

little easier a special line indicator is

used for messages, it is the asterick (*).

This gives a max. message length of 27

characters. If more is required then

unfortunately 2 lines will be needed. The

end delimiter for a message is either an

asterick or the first non-space characters

working back from the end of the line.

eg 001*THIS IS A MESSAGE

002* THIS IS A MESSAGE

003** THIS IS A MESSAGE

Line 3 will be assembled THIS IS A

MESSAGE *, only the first and last * are

message delimiters, the rest are part of the

message*

If a label is required for a message then

you must use the EQU $ (OPCODE OPERAND)

eg 001 MES1 EQU $

002 *THIS IS A MESSAGE

003 LD HL,MES1

In the above example the register set HL

will be loaded with the address of the

memory location that contains the first

letter of the message.

DELETE COMMAND

There are 3 forms of the DELETE command.

They are :-

D<RETURN> - Delete the line pointed to by

the CURRENT LINE POINTER. The CURRENT LINE

POINTER will now point to the line below the

one just deleted except in the case of the

line deleted being the last line In the

source buffer, in which case it will point

to the one above.

Dnnn<RETURN> - Delete line nnn

Dnnn:Mm<RETURN> - Delete lines nnn and mmm

and all lines inbetween.

*** WARNING

Whenever a single line is deleted an

automatic line renumber is done, so all the

lines below the line you deleted will now be

one number less, so if you wish to delete

say lines 15, 24, 38 and 67 then start with

the highest number and work down eg. delete

67 first and 15 last. If 15 is deleted first

then line 24 will now be line 23 and a

D24<RETURN> will delete the wrong line.

EDIT COMMAND

There are 3 forms of the EDIT MODE. They

are :-

E<RETURN> - edit line currently pointed to

by the CURRENT LINE POINTER.

Ennn<RETURN> - edit line nnn.

Ennn:mmm<RETURN> - edit line nnn and mmm and

all lines in between. In this mode, after

you have edited a line press <RETURN> and

the next line to be edited will be

displayed.

In all the EDIT MODES pressing <CTRL> +

<BREAK> will end the EDIT MODE for that line

and cancel any changes that may have been

made.

LIST COMMAND

There are 5 types of LIST COMMANDS. They

are :-

L<RETURN> - list all lines

Lnnn<RETURN> - list line nnn.

Lnnn:-<RETURN> - list from line nnn to the

end of the source.

L-.nnn<RET(JRN> - list all line from the

beginning to and including line nnn

Lnnn:mmm<RETURN> - list lines nnn and mmm

and all lines in between.

in all the multiple line listings the

following keys will have the following

functions :-

<S> - slow listing down

<F> - speed listing up

<H> - hold listing

<C> - continue listing after a hold <H>.

<CTRL> + <BREAK> - exit list mode.

FIND COMMAND

Fstring<RETURN> - will search through the

source file and find the first occurence of

the string. It will list the line and then

ask NEXT (Y=N). If you wish to find the next

string press Y if not press N and you will

be returned to the command mode. Using

F<RETURN> with no string will find the first

occurance of the string last asked for

starting the search from the line pointed to

by the CURRENT LINE POINTER. The string can

be a max. of 8 characters.

TAPE SAVE

TS:name<RETURM> - this command is used to

save your source file to tape for later

retrieval. The name can be a max. of 8

characters long and must start with an

alphabetical character.

TAPE LOAD

TL<RETURN> - this will load a source file

from tape into memory. No name is allowed as

the program will not search for a file but

will load the first file it comes to. The

name of the file being loaded will be

displayed on the bottom line.

TAPE VERIFY

TV<RETURN> - this command is used to verify

that a source file has been saved correctly.

At in the TL command no name Is allowed or

searched for. It is used only to verify

tapes made with the TS command, not the TO

command.

TAPE MERGE

TWRETURN> - this command will merge a

source file on tape with the one that is

currently in memory. As in TL and TV no name

is allowed or searched for. This command

allows a library of useful routines to I>e

built up and then merged Into a source file

as required.

TAPE OBJECT

TO:name<RETURN> - This command will write an

object tape (the actual machine language

program). The program will auto execute when

loaded back into the VZ-200 either with the

CRUN or CLOAD command. This command can be

used only after the source program has been

assembled and provided that no source lines

have been edited, deleted or inserted. If

the source has been modified in any way a

REASSEMBLY REQUIRED error will be given.

ASSEMBLE

A<RETURN> - this command will assemble the

program. The program will be assembled

starting from the first free byte after the

source file but it will be assembled In

reference to the value set by the ORGIN

COMMAND, this is the address that the

program will load at and excute at when it

Is loaded back into the VZ-200 as an object

tape.

ORIGIN COMMAND

Onnnn<RETURN> - set the origin for the

assembled program to nnnn.

O<RETURN> - this will set the origin to the

first free byte passed the source file. If a

program is assembled here then it can be run

with the EDITOR ASSEMBLER still In memory.

Provided you do not touch any memory below

that set by the ORIGIN COMMAND then you may

jump back to the EDITOR ASSEMBLER at 31488

(7BOOH) and your source file will still be

Intact.

RUN COMMAND

R<RETURN> - This command will run the

assembled program provided 2 requirements

are met. It any lines have been edit,

deleted or inserted since assembly you will

reckeieve a REASSEMBLY REQUIRED error. If the

ORIGIN Is not set to the first free byte

after the source code using the O<RETURN>

command then you will get a WRONG ORIGIN FOR

RUN error. After running your program you

may re-enter the EDITOR ASSEMBIFR by doing a

jump to 31488 (7BOOH). Remember the first

free byte after the source code is

constantly changing as you enter source

lines so if you wish to test run your

programs using the R command use the 0

command before every assembly. You will be

prompted SURE CY-N) if everything Is correct

to run the program.

W A R N I N G

Always save your source file before test

running a program in memory as often the

slightest mistake will cause a program crash

which will result in one of two things, one

the computer will become locked up, and you

will have to turn it off and on again to

gain control or the computer will reset

Itself. In either case you will have to load

the EDITOR ASSEMBLER again along with your

saved source file.

SET PARAMETERS COMMAND

S<RETURN> - set parameters to default value

SNABC<RETURN> - Set parameter N to the

number given (1-3) and turn A, 8, and C on.

Not all four parameters need be given when

this command is used but if they are not

given then they will be reset to there

default value

The default value for the parameters are

N 1

A OFF

B OFF

C OFF

The parameters above are used to set

certain assembly and listing options.

ASSEMBLY AND LISTING OPTIONS

Four options can be set for assembly and

listing with the SET command from the editor

or the colon (command line) during the

assembly of a program. The parameters and

their meanings are

PARAMETER A. If this Is set ON then the

assembler will list all lines and their

corresponding assembled code. If this is set

OFF then only lines with errors will be

listed.

PARAMETER B. If this is set ON then the

assembler will halt on an error and wait for

you to press the <C> key before continuing.

PARAMETER C. If this is set ON then any

lines listed during a LIST COMMAND or an

ASSEMBLE COMMAND will also be sent to the

printer.

PARAMETER N. N can be either 1, 2 or 3

and will decide how the assembler handles

the assembly of messages.

N=l - all messages will be assembled in

ASCII format eg 0=48, A=65

N=2 - all messages will be assembled with

bit 6 set off. eg 0=48, A=I. This will give

you white characters on a black background

if they are written directly to the screen.

N=3 - all messages will be assembled with

but 6 set on. eg. 0=112, A=65. This will

give you black characters on a white

background if they are written directly to

the screen.

NOTE :- if you are going to use the

VZ-200 rorn calls listed in APPENDIX B to

send characters to the screen then assemble

characters In ASCII format (N=I).

A fifth option can be used with the colon

(command line) during an assembly. This Is

the H option which will simple cause a

forced halt in assembly until you press the

<C> key. A command line may be used to set

parameters or force a halt but it may not do

both.

EXAMPLE USE OF C AND LINES

001 TEST LD HL,7000H

002 LD DE07001H

003:AC

004 LD BC,IFFH

005 LD (HL),32

006:A

007 LDIR

OOB XOR A

009:H

010 LD (26624)RA

Oil JP 7BOOH

Line 3 will turn parameters A and on.

This means that lines from now on will be

listed to the screen (A) and also sent to

the printer (C). Line 6 will turn option C

off so lines will still be sent to the

screen but not the printer. Line 9 causes a

halt in assembly until the <C> key is

pressed.

STATUS LINE (TOP LINE)

The top line is the status line Is shown

ln inverse to the rest ol the screen. It

shows free memory (FM), the currently set

origin (ORG) and the state of the parameters

(SPAR). The parameter N will be shown (a

number from 1 to 3) and if A, B or C Is on

then their letter will be shown.

For example, if free memory equals 10500,

the currently set orgin Is 32000, N=2, A=on,

B=off and C=on then the top line will be

FM:10500 ORG:32000 SPAR:2A C

Whenever there is a hold on a listing

(H), a forced halt in an assembly (:H) or a

hold on error status situation then the top

line will flash to show you that the program

is waiting for you to press the <C> key.

INTERPRETATION OF NUMBERS

The ASSEMBLER recognises both decicmal

and hexadecimal numbers. All numbers must

start with a digit else it will be

interpreted as a label. All hex. numbers

must end with the prefix H. EXAMPLES

100 100 in decimal

IOOOH 1000 in Hex. (equal to 4096 in

decimal)

65535 = 65535 In decimal

OFFFFH = FFFF in Flex. (equal to 65535 in

decimal)

ARITHMETIC OPERATIONS

The ASSEMBLER is capable of only

performing addition and subtraction and then

only once in any equation. EXAMPLES

100+10

1000H+OAFOH

TES1+1245

234-12

10-2300

1089H-TES1

TES1+TES2

All the above are legal with TESI and

TES2 being labels. The following 2 examples

are not legal because there is more then one

operation.

120+2300-12

TEST+123+12

A P P E N D I X A

OPCODES RECOGNISED

BY THIS ASSEMBLER

ADC DAA IM LDI RES RRCA

ADD DEC IN LDIR RET RRD

AND DEFB INC NEG RETI RST

BIT DEFS IND NOP RETN SBC

CALL DEFW INDR OR RL SCF

CCF DI INI OTDR RLA SET

CP DJNZ INIR OUIR RLC SLA

CPD El JP OUT RLCA SRA

CPDR EQU JR OUTD RLD SRL

CPI EX LD OUT] RR SUB

CPIR EXX LDD POP RRA XOR

CPL HALT LDDR PUSH RRC

A P P E N D f X B

USEFUL ROM CALLS

SCAN KEYBOARD

CALL 2EF4H

All registers are used and on return A

reg. will hold the ASCII equivalent to the

key pressed, 0 If no key pressed. See

example program one.

OUTPUT CHARACTER TO VIDEO

CALL 33AH

On entry A reg. holds ASCII equivalent of

character to display. Ali registers are

preserved.

OUTPUT MESSAGE TO VIDEO

CALL 2B75H

On entry HL registers must point to the

start of the message and the message must be

terminated by a zero byte. All registers are

used.

CLEAR SCREEN

CALL 109H

All registers are used.

GENERATE SOUND

C@LL 345CkA

On entry HL registers contain the pitch

and BC registers contaln the duration. All

registers are used.

GENERATE BEEP

CALL 3450H

This routine generates the beep heard on

pressing a key in normal VZ-200 BASIC. All

registers except HL are used.

SEND CHARACTER TO PRINTER

CALL 58DH

On entry C register contains the ASCII

equivalent of the character to be printed.

All registers are used.

CHECK PRINTER STATUS

CALL 5C4H

Only the A register is used and on return

if A = I then the printer is busy or if A

0 then the printer is not busy.

TAPE ROUTINES

TAPE FORMAT.

LEADER - this is a block of 255 80H bytes

followed by 5 OFEH bytes.

COMMAND BYTE - this byte tells the VZ-200

what to do after loading the program. All

basic programs are saved with a OFOH byte. A

OFIH byte will make the program auto execute

starting at the first address of the loaded

block. This is the command byte that the

EDITOR ASSEMBLER places on Its OBJECT tapes.

NAME OF PROGRAM - This will be up 16

characters long and terminated with a zero

byte.

DELAY - After the name is placed on the tape

there is a short delay. This is placed here

to allow the computer to check the name on

the tape against the name of the program you

wish to load. The delay is obtained with the

following short program.

001 LD BC,019AH

002 RPT DEC BC

003 LD A,B

004 OR C

005 JP NZ,RPT

START ADDRESS - This Is the beginning

address of the block to load.

END ADDRESS - This Is the end address of the

block to load.

DATA - This Is the block of data to load.

CHECKSUM BYTES - This Is the next 2 bytes

after the data and must be the same as the

checksum of the data just loaded. The

checksum starts with the first byte of the

START ADDRESS and finishes with the last

byte of the DATA. As the tape is being

loaded it is stored in a 2 byte buffer

pointed to by the IX regs. The buffer used

1 2

by BASIC is at 7823/4H.

TRAILER - this is 14 zero bytes which. follow

the checksum bytes.

SAVE PROGRAM

CALL 34A9H

On entry the start of the block of memory

to save must be loaded into 7BA4/5H (start

of basic pointer) and the end of block to be

saved must be placed in 7SF9/AH (end of

basic pointer). The HL regs. must point to

the name to be given to the saved program.

The name must start and finish with a quote

(11). Only the first 16 characters will be

used. The program Kill be saved with the

command byte of OFOH. If you want this to be

different than load C register with your new

command byte and do a DI instruction and

then CALL 34ACH

LOAD PROGRAM

CALL 365FH

Before calling the HL regs. must point to

the name of the program to load with the

name starting with a quote (11) and ending

with a quote (11). Only the first 16

characters will be used and they will bs

transferred Into a buffer starting at 7A9DH

with the length being stored In location

7AD6H. If you wish the first program to be

loaded regardless of name then the HL regs.

must point to either a 3AH or 0 byte.

LOAD NAME

CALL 358CH

This routine will load a name pointed to

by the HL regsinto a 16 byte buffer at

loaction 7A9DH and store the length of the

name at location 7AD2H. The name must start

and finish with a quote (11). Only the first

16 characters will be used.

WRITE LEADER

CALL 3558H

This routine will write a leader, a

command byte and the name to tape. The name

must be loaded as In the LOAD NAME ROUTINE.

C reg must contain the command byte.

FIND LEADER

CALL 35EIH

This routine will search for a leader,

and specific name. The name to find must be

loaded as in the LOAD NAME ROUTINE. The

command byte found after the leader will be

stored In location 7AD2H. WARNING - It will

not return till the name is found.

FIND START/END

CALL 3868H

This routine Is called after finding the

leader and name and will return with the

start address of the block to load in the DE

regs and the end address of the block to

load in the HL regs. Before calling the IX

regs must be loaded with address of a 2 byte

buffer which will be used for the checksum

test at the end of the program load. Basic

uses locations 7823/4H ie load IX with

7823H.

READ BYTE

CALL 3775H

This routine will return with the next

byte found on a tape in the A reg. If no

byte is found within a specific time period

then the routine will return with the Carry

Flag set. All registers are preserved.

WRITE BYTE

CALL 3511H

This routine will write the byte in the A

reg to tape. All other registers are

preserved.

CHECKSUM ADD

CALL 388EH

This routine adds the A reg to the 16 bit

value pointed to by the IX regs.

JUMP TO BASIC

JP lAl9H

The OBJECT TAPES written by this EDITOR

ASSEMBLER will auto execute when loaded back

into the computer. This Is fine for programs

like this EDITOR ASSEMBLER but there may be

times when you wish to load sub-routines

Into high memory which will then be called

from a BASIC program. To get your object

tape to return to basic after it has loaded

just make the first Instruction a JP IA19H.

EXTRA INFORMATION

The VZ-200 TECHNICAL REFERENCE MANUAL Is

another essential toot for the budding

assembly language programmer. It contains

information on the memory map, interfacing

with the keyboard and video display, as well

as other useful ROM routines.

Another good book for general Z-80

programming is HOW TO PROGRAM THE Z-80 by

RODNAY ZAKS. This book describes all the

Z-80 opcodes with a good description of what

they do and how they effect the FLAG

another essential requisition.