Difference between revisions of "Peripheral 3 Register"

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(core 3.0 changes)
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(R/W) 0x08 (08) => Peripheral 3 setting:
 
(R/W) 0x08 (08) => Peripheral 3 setting:
   bit 7 = 128K paging enable (inverse of port 0x7ffd, bit 5)  
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   bit 7 = Unlock(1)/lock(0) port $7FFD paging (read 1 indicates port $7FFD is not locked)
          Unlike the paging lock in port 0x7ffd,
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   bit 6 = 1 to disable RAM and I/O port contention (soft reset = 0)
          this may be enabled or disabled at any time.
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   bit 5 = AY stereo mode (0 = ABC, 1 = ACB) (hard reset = 0)
          Use "1" to disable the locked paging.
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   bit 4 = Enable internal speaker (hard reset = 1)
   bit 6 = "1" to disable RAM contention. (0 after a reset)  
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   bit 3 = Enable 8-bit DACs (A,B,C,D) (hard reset = 0)
   bit 5 = Stereo mode (0 = ABC, 1 = ACB)(0 after a PoR or Hard-reset)
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   bit 2 = Enable port $FF Timex video mode *read* (hides floating bus on 0xff) (hard reset = 0)
   bit 4 = Enable internal speaker (1 = enabled)(1 after a PoR or Hard-reset)
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   bit 1 = Enable Turbosound (currently selected AY is frozen when disabled) (hard reset = 0)
   bit 3 = Enable Specdrum/Covox (1 = enabled)(0 after a PoR or Hard-reset)
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   bit 0 = Implement Issue 2 keyboard (port $FE reads as early ZX boards) (hard reset = 0)
   bit 2 = Enable Timex modes (1 = enabled)(0 after a PoR or Hard-reset)
 
   bit 1 = Enable TurboSound (1 = enabled)(0 after a PoR or Hard-reset)
 
   bit 0 = Reserved, must be 0
 
  
https://www.specnext.com/tbblue-io-port-system/
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The Timex modes are operational even when bit 2 is set to zero, you can still write to port $FF with desired mode changes. Bit 2 does only enable readability of port $FF.
  
'''NEW in core 3.0:'''
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When loading 48k SNA files through NextZXOS, be aware it does lock down many features of Next to better simulate ZX48 machine, including lock of {{PortNo|$7FFD}} paging feature. If you are using 48k SNA file for convenience, but you are actually using full ZX Next features, make sure you enable/unlock all relevant bits, before using the particular feature.
 
 
bit 4 default 0
 
bit 0 set selects issue 2 keyboard
 

Latest revision as of 00:05, 16 April 2020

Number $08
Readable Yes
Writable Yes
Short Description ABC/ACB Stereo, Internal Speaker, SpecDrum, Timex Video Modes, Turbo Sound Next, RAM contention and [un]lock 128k paging.

(R/W) 0x08 (08) => Peripheral 3 setting:

 bit 7 = Unlock(1)/lock(0) port $7FFD paging (read 1 indicates port $7FFD is not locked)
 bit 6 = 1 to disable RAM and I/O port contention (soft reset = 0)
 bit 5 = AY stereo mode (0 = ABC, 1 = ACB) (hard reset = 0)
 bit 4 = Enable internal speaker (hard reset = 1)
 bit 3 = Enable 8-bit DACs (A,B,C,D) (hard reset = 0)
 bit 2 = Enable port $FF Timex video mode *read* (hides floating bus on 0xff) (hard reset = 0)
 bit 1 = Enable Turbosound (currently selected AY is frozen when disabled) (hard reset = 0)
 bit 0 = Implement Issue 2 keyboard (port $FE reads as early ZX boards) (hard reset = 0)

The Timex modes are operational even when bit 2 is set to zero, you can still write to port $FF with desired mode changes. Bit 2 does only enable readability of port $FF.

When loading 48k SNA files through NextZXOS, be aware it does lock down many features of Next to better simulate ZX48 machine, including lock of Memory Paging Control ($7FFD / 32765) paging feature. If you are using 48k SNA file for convenience, but you are actually using full ZX Next features, make sure you enable/unlock all relevant bits, before using the particular feature.