Zenith Data Systems (ZDS) ZBIOS 'MFM-300 Monitor' reverse engineering.

Multi-Function Monitor (MFM) was a build-in SoftIce/Periscope like Debugger/Monitor Bios extension user could enter with a press of a button (CTRL-ALT-ENTER) at any time.

CTRL-ALT-ENTER displays the contents of the CPU's registers and flags, and then enters the Monitor program. Press G and ENTER to return to the operating system or your software program.

Description in Zenith Z386SX (3557V4) Owners Manual page 88, Zenith Z-386SX/20 (3797V1) Owners Manual page 106. REMark 'The Official Zenith/Heath Computer User Magazine' volume10-issue10-1989 page 11 and volume10-issue12-1989 page 25.

MFM Monitor menu:

		ENTER YOUR CHOICE:

	- MFM-300 Command Summary -
CMD:	Explanation		Syntax
----	-----------		------
?:	Help			?
B:	Boot from disk		B [{F|W}][{0|1|2|3}][:<partition>]
C:	Color bar		C
D:	Display memory		D [<range>]
E:	Examine memory		E <addr>
F:	Fill memory		F <range>,{<byte>|"<string>"}...
G:	Execute (Go)		G [=<addr>][,<breakpoint>]...
H:	Hex math		H <number1>,<number2>
I:	Input from port		I <port>
M:	Move memory block	M <range>,<dest>
O:	Output to port		O <port>,<value>
R:	Examine Registers	R [<register>]
S:	Search memory		S <range>,{<byte>|"<string>"}...
T:	Trace program		T [<count>]
U:	Unassemble program	U [<range>]
V:	Set Video/Scroll	V [M<mode>][S<scroll>]
	Where <range> is:	<addr>{,<addr>|L<length>}
TEST:	Extended diagnostics	TEST
SETUP:	Define hardware Setup	SETUP

TEST menu:

		CHOOSE ONE OF THE FOLLOWING:

		1. DISK READ TEST
		2. KEYBOARD TEST
		3. BASE MEMORY TEST
		4. EXTENDED MEMORY TEST
		5. POWER-UP TEST
		6. EXIT

Z-386 MFM-300 Monitor, Version 3.2C POST code list, crude decompiled listing and IDA 6.1 dump. I forgot to relocate binary to F000 before starting dissasembly and now I dont know how to change it post facto :(, means few jumps to raw F000 pointers show up as red. If you know how to fix it please drop me a hint :)

MFM Monitor shipped in models from three generations of Zenith computers.

386:

286:

8080:

Zenith Data Systems (ZDS) Z-159 MFM-1200 Monitor, Version 2.9
Live Zenith Z-150 running in the browser MFM-150 Monitor v3.1E

raszpl/Zenith_ZBIOS

Zenith Data Systems (ZDS) ZBIOS 'MFM-300 Monitor' reverse engineering.