Difference between revisions of "Next Memory Bank Select"

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(adding info)
(core 3.1.4 changes/refresh)
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|PortMask=%1101 1111 1111 1101
 
|PortMask=%1101 1111 1111 1101
 
}}
 
}}
bits 3:0 = most significant bits of the 16K RAM bank selected in {{PortNo|$7FFD}}
+
: bit 7 = 1 to set pentagon 512K mode (hard reset = 0) †
 +
: bits 3:0 = most significant bits of the 16K RAM bank selected in {{PortNo|$7FFD}}
  
 
Port 0xDFFD bits 3:0 are combined as the highest bits with the bank selected in port 0x7FFD to form a 7-bit bank number.
 
Port 0xDFFD bits 3:0 are combined as the highest bits with the bank selected in port 0x7FFD to form a 7-bit bank number.
 +
 +
† Pentagon 512K mode is applied only when the machine is set to pentagon timing ({{NextRegNo|$03}}). In this mode the selected 16K bank comes from port 0x7ffd {bits 7:6, bits 2:0}

Revision as of 00:51, 16 April 2020

Number $DFFD
Decimal
Short desc. Provides additional bank select bits for extended memory.
Bit Mask %1101 1111 1111 1101
Readable No
Writable Yes
Subsystem Memory map
bit 7 = 1 to set pentagon 512K mode (hard reset = 0) †
bits 3:0 = most significant bits of the 16K RAM bank selected in Memory Paging Control ($7FFD / 32765)

Port 0xDFFD bits 3:0 are combined as the highest bits with the bank selected in port 0x7FFD to form a 7-bit bank number.

† Pentagon 512K mode is applied only when the machine is set to pentagon timing (Machine Type Register ($03)). In this mode the selected 16K bank comes from port 0x7ffd {bits 7:6, bits 2:0}