Date   : Mon, 29 Apr 2002 18:07:24 +0100
From   : "Richard Gellman" <r.gellman@...>
Subject: Completely stuck on tube emulation

I'm working on 6502 Second processor emulation, and I've hit a brick wall.

This is the output I'm getting:

Acorn TUBE 6502 64K

Acorn 1770 DFS

COMAL

]RANDOM_COMMAND
AND nVAL (MOD  LIST LN NEW DEG ASN nREPEAT ACS @)iAND $PI e$AND $ACS
e$EXP VAL  REF NEW UNTIL PI END TAN STR$  }RAD ACS RUN DIV   3
REPEAT ACS $ ACS  LOG VAL  TO RAD  UNTIL INT VAL (8$PI ebAND bEXP DEG
 EXEC random_command
      ^
]

(I'm using COMAL, because BASIC just hangs when you type anything except a *
command)

I've checked out the following:
The second processor emulation is coded identical to the base processor
core.
The addressing modes are exact as they should be.
Relative cycle counts are as they should be (2nd: 3Mhz, Base: 2Mhz).
IRQ/NMI timing is correct.
ROM/RAM selection on startup is correct.
The language code is not corrupted.
The effects are the same with each Tube ROM image i've tried.
The TUBE interface is emulated exactly according to the information in
Acorn's Application Note 004 (The Tube).
The language ROM works fine without the second processor emulation.
The language ROM has been tested on an actual Master 128 with 6502 Second
Processor, and works fine.
There are no conflicts between variable names in the emulation source code.

I've checked the code back and forth about 6 times now, and there is
absolultely nothing wrong anywhere.
Yet, it still doesn't work :(

(Note: Although you do get a prompt back, and although in Model B mode,
BASIC II accepts commands, the system still refuses to run "stable". Any
attempt to load anything in model B mode when specifying load address
results in a hang, and programs do not work correctly in Master 128 mode. In
particular Acornsoft EDIT starts and appears to work fine, but all function
key commands just result in "Press ESCAPE to contiue".)

If anyone has any possible ideas as to what is wrong, no matter how
insignificant or daft they may seem.. please do let me know :)

-- Richard Gellman

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