Master CMOS checksum

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
dominicbeesley
Posts: 383
Joined: Tue Apr 30, 2013 11:16 am

Master CMOS checksum

Postby dominicbeesley » Tue Sep 19, 2017 10:49 pm

I've been trying to figure out how the Master 128 checksums its CMOS settings. All I've found so far is this which has been very helpful
but doesn't mention the actual checksum http://beebwiki.mdfs.net/CMOS_configura ... allocation

So I'm guessing the checksum is at location 50, does anyone know which checksum algorithm was used?

Also, does anyone know why Acorn didn't use the PS (power sense) input to monitor battery, according to the data sheet it requires a resistor/capacitor only and will set a bit if the power fails...

D

User avatar
jgharston
Posts: 2658
Joined: Thu Sep 24, 2009 11:22 am
Location: Whitby/Sheffield

Re: Master CMOS checksum

Postby jgharston » Fri Sep 22, 2017 2:08 am

dominicbeesley wrote:I've been trying to figure out how the Master 128 checksums its CMOS settings.

The 8-bit systems don't checksum the CMOS, only the ARM systems do and even then not all of them. Location 50 doesn't hold a checksum, location 50 is just another location on systems that have more than 50 locations.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

dominicbeesley
Posts: 383
Joined: Tue Apr 30, 2013 11:16 am

Re: Master CMOS checksum

Postby dominicbeesley » Fri Sep 22, 2017 11:49 am

Thanks JGH, I was misremembering "Bad Sum" as being config rather than ADFS...it's my age

User avatar
jgharston
Posts: 2658
Joined: Thu Sep 24, 2009 11:22 am
Location: Whitby/Sheffield

Re: Master CMOS checksum

Postby jgharston » Sat Sep 23, 2017 12:43 am

dominicbeesley wrote:Thanks JGH, I was misremembering "Bad Sum" as being config rather than ADFS...it's my age

Hey, I can barely remember what I was doing when I... what was I saying?

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

User avatar
1024MAK
Posts: 6667
Joined: Mon Apr 18, 2011 4:46 pm
Location: Looking forward to summer in Somerset, UK...

Re: Master CMOS checksum

Postby 1024MAK » Sat Sep 23, 2017 9:32 am

jgharston wrote:
dominicbeesley wrote:Thanks JGH, I was misremembering "Bad Sum" as being config rather than ADFS...it's my age

Hey, I can barely remember what I was doing when I... what was I saying?

You may want to get the DRAM refresh system checked out... :lol:

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
BeebWiki‬ - for answers to many questions...


Return to “hardware”

Who is online

Users browsing this forum: No registered users and 12 guests