Difference between revisions of "OSBYTE &6F"

From BeebWiki
Jump to: navigation, search
m (Added Integra-B info.)
(Added ROMSTROBE information.)
Line 1: Line 1:
 
[[Category:OSBYTE]]
 
[[Category:OSBYTE]]
OSBYTE &6F (111) - Read/Write Aries/Watford Shadow RAM Switch
+
===OSBYTE &6E (110) - Write to ROMSTROBE===
  
    On entry:
+
  On entry:
     X b7=0 no stack operation
+
     X= new ROMSTROBE value
      b7=1 pop state from stack (reading), push state on stack (writing)
+
  On exit:
      b6=0 write switch state
+
     X= old ROMSTROBE value
      b6=1 read switch state
 
      b0=0 select video RAM
 
      b0=1 select program RAM
 
    On exit, X contains the previous switch state:
 
      b0=0 video RAM
 
      b0=1 program RAM
 
   
 
    This gives the following entry and return values:
 
     X=&00 - Select video RAM
 
      &01 - Select program RAM
 
      &40 - Read current RAM state
 
      &41 - Read current RAM state
 
      &80 - Save current RAM state and select video RAM
 
      &81 - Save current RAM state and select program RAM
 
      &C0 - Pop and select stacked RAM state
 
      &C1 - Pop and select stacked RAM state
 
  
This call is implemented by the Watford and Aries shadow memory systems for
+
The value passed in X is written to the ROMSTROBE port and the RAM copy, the
the BBC B computer, and compatible systems. The B+, Integra-B and Master
+
old value of the RAM copy is returned. Implemented in the Electron Plus 1
series use different shadow selection calls.
+
Support ROM. The ROMSTROBE port is at &FC73 on the Electron, and writes
 +
the byte of data while the ROMSTROBE line is activated on the cartridge
 +
slot.
 +
 
 +
 
 +
===OSBYTE &6E (110) - Early Watford DFS double-step control===
 +
 
 +
Do not use - use *OPT40,n and *OPT80,n.<ref>''The Micro User'', August 1986, p.22.</ref>
  
 
==See Also==
 
==See Also==
* [[OSBYTE &49]] - Check for Integra-B shadow memory
 
* [[OSBYTE &6C]] - Select Master/Integra-B shadow memory
 
* [[OSBYTE &6F]] - Select BBC B shadow memory
 
* [[OSBYTE &70]] - Select memory for Master VDU access
 
* [[OSBYTE &71]] - Select memory for Master video display
 
* [[OSBYTE &72]] - Select future use of shadow memory
 
* [[OSBYTE &73]] - Select shadow bank
 
* [[OSBYTE &74]] - Check for Solidisk shadow memory
 
* [[Paging in video memory]]
 
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
 
* http://mdfs.net/Docs/Comp/BBC/Osbyte00
  
[[User:Jgharston|Jgharston]] ([[User talk:Jgharston|talk]]) 20:28, 3 April 2015 (UTC)
+
==References==
 +
<references />
 +
 
 +
[[User:Jgharston|Jgharston]] 21:17, 26 May 2009 (UTC)

Revision as of 02:15, 14 January 2016

OSBYTE &6E (110) - Write to ROMSTROBE

 On entry:
   X= new ROMSTROBE value
 On exit:
   X= old ROMSTROBE value

The value passed in X is written to the ROMSTROBE port and the RAM copy, the old value of the RAM copy is returned. Implemented in the Electron Plus 1 Support ROM. The ROMSTROBE port is at &FC73 on the Electron, and writes the byte of data while the ROMSTROBE line is activated on the cartridge slot.


OSBYTE &6E (110) - Early Watford DFS double-step control

Do not use - use *OPT40,n and *OPT80,n.[1]

See Also

References

  1. The Micro User, August 1986, p.22.

Jgharston 21:17, 26 May 2009 (UTC)