24

CONCLUSION

AH tke commands of the MONITOR have now been demonstrated,
and you are ready to start writing and running your own machine
code programs.

The Spectrum MONITOR can be used on its own to enter Machine
code programs, but to simplify the process of Machine code
programming, PICTURESOVUE also market an EDITOR
ASSEMBLER that is fully compatible with the MONITOR, and
which allows you to enter ZBO mnemonics into a listing, with line
numbers and Labels, The listing is totally independent from Basic
and uses a unigue 40 column Screen display.

If you own a 48K Spectrum, the ASSEMBLER and tho MONITOR
can both reside in memory together, creating the most versatile
Machine code system available for the ZX Spectrum. The
ASSEMBLER is also designed to make the best use of available
memory in a 16K Spectrum.

m o — D
APPENDIXA | (CPU REGISTERS

The values in the CPU registers are stored in the following locations
after a Breakpoint, and can be altered using the M command. The
alterations only take effect if the Breakpoint Continue (C)
command or a Jump (J) command is used to access the machine
code. '

bk šek o REG,

7F3D —- FE3ZD- R /
7F3E — FF3E--.!

7F3F — FEZFE — F'
7F40 — FF40 — A'
JFAi— FMi-C'
7F42- FF42— B'
7F43 — FF43— E'
7F44 — FF44 — D'
745 - FF45- .L'"
7F46 — FF46G—- H'

7F47 — FF47— F
7F48—- FF48— A
7F49 — FF49— C
TF4A — FF4A- B . '
JF4AB—- FFA4AB- E
7F4C— FF4C— D
7F4D — FF4D— L
TF4E — FF4E-— H

7FAF — FF4F — IX (Low)
7F50 — FFS50— 1X (High)
7F51 — FF51— 1Y (Low)
7F52— FF52— IY (High) h
7F53 — FFF53— SP (Low) ;
7F54 — FF54— SP (High)
7F55 — FF55— PC (Low)
7F56 — FF56 — PC (High)

Any changes to the | and 1Y registers may cause the ZX
SPECTRUM to crash. o Sa