Difference between revisions of "Plus 3 Memory Paging Control"

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(core 3.0 changes)
Line 12: Line 12:
 
! Bit !! Effect  
 
! Bit !! Effect  
 
|-
 
|-
| 5-7 || Undocumented, may be used for extra bits of slot 4 bank select (see {{PortNo|$7FFD}})
+
| 7-3 || Unused, use 0 (Printer Port Strobe b4 and Disk motor enable b3 are not implemented in core3.0)
|-
 
| 4 || Printer Port Strobe
 
|-
 
| 3 || Disk motor enable
 
 
|-
 
|-
 
| 2 || Normal mode: High bit of ROM selection.
 
| 2 || Normal mode: High bit of ROM selection.

Revision as of 05:41, 4 October 2019

Number $1FFD
Decimal
Short desc. Controls ROM paging and special paging options from the +2a/+3.
Bit Mask %0001 ---- ---- --0-
Readable No
Writable Yes
Subsystem Memory map

Bit mapped to control paging options.

Bit Effect
7-3 Unused, use 0 (Printer Port Strobe b4 and Disk motor enable b3 are not implemented in core3.0)
2 Normal mode: High bit of ROM selection.

Special mode: High bit of memory configuration number (see Memory map).

1 Special mode: Low bit of memory configuration number.
0 Paging mode. 0=Normal, 1=Special.

Any values written to this port should also be stored in $5B67 if you intend to use any OS routines.

NEW in core 3.0:

When exiting +3 special paging mode, the banks 5 and 2 are mapped back at regular place.