Difference between revisions of "Peripheral 3 Register"

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.

@@ Line 6: / Line 6: @@
 }}
 (R/W) 0x08 (08) => Peripheral 3 setting:
-   bit 7 = Unlock(1)/lock(0) port $7FFD bit 5 (read 1 indicates port $7FFD is not locked)
+   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* (disables floating bus on 0xff) (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)
@@ Line 17: / Line 17: @@
 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:'''
+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
-- needs clarification from core team, two documents about core3.0 registers I have available contradict each other, but I guess the "0" is the correct default and the "1" in table above is obsolete setting.