20

Vf you have made a typing error, or if YOu want to put another
message at a new starting eddress, type $, to re-enter the $ "
command at the beginning, in the sarne way that the 'M' command
is re-entered. You wili have to enter the new address before making
Your corraction, or starting your new message.

The repeating keyboard with the fast seroliing sereen works as in the
M' command, to allow you to review a message guickly.

Remember that, having entered the starting address, the escape
command is accessed by typing STOP (Symbol Shift and A).

Z — Disassembler

This command will disassemble any part of RAM or ROM, either to
the screen alone, or to both the screen and the ZX Printer. It
provides a display that includes the Hex address of the first byte of
the instruction, the Hex values of the bytes that relate to that
instruction and the ZB0 mnemonic for that instruction, The fuli set
of Z80 mnemonics can be disassembled.

The command takes the form: "Z aaaa bbbb' where 'Z' is the "

|. command mode, 'aaga' is the hex starting address and 'bbbb' is the

hex end address of the part of memory you wish to disassemble.

Type Z to access the command.
Type 0000 the address of the start of the ROM.
Type 0020 the end address,

Having typed in the end address, the screen will seroll and display.
PRINTER?

Your response to this is similar to the Basic "Seroll?" command. 1f
you wish to use the printer, type ENTER; but if you only reguire a
screen display, type 'N' (for NO).

Type N for screen display only.

The disassembly will appear on the screen thus:

>Z0000 OO20

FRINTER?
0000 FZ DI
0001 AF XOR

;
0002 11FFFF  LD  DE,FFFF

a Pa

21

0005. C30B11 JP. 11CB O.
0008 2ZAŠDSC  LD HL, (5C5D)
OOOB ZZSESC UD . (SČSF),HL

OOOE 1843 JR 0053
0010 C3F215 JE 155:2
0013 FE RST :.SB

0014 FE RSi S

0015 FE . RST'. 3B

0016 FF be RSI... SB

0017 FF tARSTIO .
0018 ZASDSC. — LD HL, (SCS5D)
OO1B ZE . LD A, (HL)

001C CD7DO0OO CALL OO7D
ENTER for ,more; X for end

16 lines of disassembly will be displayed when using the screen only,

| followed by the message:

"ENTER for more; X for end.

Pressing ENTER wili display the next 16 lines, unless the end
address is reached, when the prompt and cursor will be returned.

Typing 'X' in response to the above message wili also return the
prompt and cursor. MM ;

V you are disassembling to the Printer, the routine will continue,
uninterrupted, until it reaches the end address, The Printer can be
stopped by using the Break key in the normal way, which will
return you to BASIC. You will then need to access the Monitor as
described on Page 2.

If you try to disassemble to the Printer when it is not connected,
the screen display will be produced on its own, the routine stopping
when it has reached the end address.

AH disassembled addresses and values are.in Hex. Relative jumps
show the address to which the jump will. go, with the offset value
shown with the hex coding. for that instruction.

The only instructions that are displayed in a slightly different form
from the published Zilog mnemonics are "JP (HLI" and the IX and
IY counterparts "JP (1X)"' and "JP (1Y)'"'. As these instructions
jump to the address 'actually held in the register, the brackets are
not shown in the display, which makes the action of the instruction
a little clearer.