| www.retrosoftware.co.uk http://www.retrosoftware.co.uk/forum/ |
|
| Shadow RAM control http://www.retrosoftware.co.uk/forum/viewtopic.php?f=73&t=641 |
Page 1 of 1 |
| Author: | RichTW [ Wed Jun 29, 2011 5:07 pm ] |
| Post subject: | Shadow RAM control |
Can anyone point me at some docs which cover how shadow RAM is controlled (at the hardware level) on both a B+ and a Master? Basically I want to make sure it's completely disabled - neither paged in nor being displayed. Will Code: LDA #0 STA &FE34 do the trick on both machines? And on a regular BBC B, what will that do? (is it mapped to FE30 or just thrown away?) Cheers! |
|
| Author: | TomW [ Wed Jun 29, 2011 6:22 pm ] |
| Post subject: | Re: Shadow RAM control |
Yes and mirrors &FE30. |
|
| Author: | RichTW [ Wed Jun 29, 2011 9:10 pm ] |
| Post subject: | Re: Shadow RAM control |
Sweet. Cheers Tom. |
|
| Author: | jgharston [ Mon Aug 08, 2011 3:23 am ] |
| Post subject: | Re: Shadow RAM control |
RichTW wrote: Basically I want to make sure it's completely disabled - neither paged in nor being displayed. MODE (positive any number less than &80)
|
|
| Author: | RichTW [ Mon Aug 08, 2011 7:04 am ] |
| Post subject: | Re: Shadow RAM control |
Not if *SHADOW has been entered beforehand! I wanted a direct hardware access solution (as I'm changing screen mode by direct poking so that the screen memory isn't cleared), and it seems that the solution which is compatible with everything is: Code: LDA #0
STA &FE34 ; disable shadow RAM LDA &F4 STA &FE30 ; put FE30 back in case it was mirrored at FE34 |
|
| Page 1 of 1 | All times are UTC [ DST ] |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|