Date : Wed, 07 Jan 2015 18:48:15 +1100
From : ajw@... (Alan Williams)
Subject: Serial console active at power-on
More apologies in advance for the lack of
attribution/mis-attribution/continuity...
Once I built a 6502 SBC with 32K ram and a 27512 ROM. The ROM was mapped as
the MOS and three Sideways roms, one was Basic the
other two ROMPAC fileing system, from which the application booted and
listened on the serial port.
I had to do a number of hacks to the MOS to deal with missing hardware (the
keyboard for a start) and the relocation of the ADC chip and various other
things.
In the mos there is a table of default values for the *FX settings, so my
approach was to edit that to give different default values for *FX2 and
*FX3.
I have found my notes from 1987. this may need some corroboration but it
looks like the rom locations in question may be as follows.
OSBYTE RAM ROM
177 &B1 241 D981 is 0 make 1 input source
181 &B5 245 D985 is 1 possibly make 0
236 &EC 27C D9BC is 0 possibly make 1 (*FX3)
245 &F5 285 D9C5 is 1 possibly make 0 (default printer)
I also found a scrap of print out showing a mod I made to the keyboard
scanner but it's not disassembled from the right address but it goes like
this.
LDY #&03
STY &FE40
LDY #&7F
STY &FE43
STX &FE4F
LDX &FE4F - Replace with LDX#0:NOP
RTS
If you are up for blowing a hacked mos chip to achieve a serial console the
above may help. You would probably also need to find and fix the default
baud rate. Mine was different hardware and was fixed by links.
Alan
-----Original Message-----
From: bbc-micro-bounces+ajw=bigblue.net.au@...
[mailto:bbc-micro-bounces+ajw=bigblue.net.au@...] On Behalf
Of J.G.Harston
Sent: Wednesday, 7 January 2015 10:50 AM
To: bbc-micro@...
Subject: Re: [BBC-Micro] Serial console active at power-on
Peter Coghlan wrote:
> Also, be careful not to just discard every attempt to send 14 through
> WRCHV.
> It could be part of a multi byte VDU sequence such as VDU 1 or VDU 31
> for example.
I thought it was obvious I was saying not to discard CHR$14, but forcible
unselect VDU 14 mode, eg:
.newWRCH
JSR oldWRCH:PHA
LDA vduStatus:AND #whatever:STA vduStatus :\ Turn VDU status off PLA:RTS
--
J.G.Harston - jgh@... - mdfs.net/jgh
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