Reset Register: Difference between revisions

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m Xalior moved page Next Reset Register to Reset Register: match formal nextreg.txt name
 
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{{NextRegister
{{NextRegister
|Number=02
|Number=$02
|Readable=Yes
|Readable=Yes
|Writable=Yes
|Writable=Yes
|ShortDesc=Identifies type of last reset. Can be written to force reset.
}}
}}
{|
Read:
! Bit
  bit 7 = 1 if the reset signal to the expansion bus and esp is asserted
! Function
  bits 6:5 = Reserved
|-
  bit 4 = 1 if multiface nmi was generated by an i/o trap (experimental, see nextreg 0xda)
| 0 | Reserved
  bit 3 = 1 if multiface nmi was generated by this nextreg
|}
  bit 2 = 1 if divmmc nmi was generated by this nextreg
  bit 1 = 1 if the last reset was a hard reset
  bit 0 = 1 if the last reset was a soft reset
  * Only one of bits 1:0 will be set
Write:
  bit 7 = Assert and hold reset to the expansion bus and the esp wifi (hard reset = 0)
  bits 6:5 = Reserved must be zero
  bit 4 = Clear i/o trap (write zero to clear) (experimental) **
  bit 3 = Generate multiface nmi (write zero to clear) **
  bit 2 = Generate divmmc nmi (write zero to clear) **
  bit 1 = Generate a hard reset (reboot) *
  bit 0 = Generate a soft reset *
  * Hard reset has precedence
  ** These signals are ignored if the multiface, divmmc, dma or external nmi master is active
  ** Copper cannot clear these bits
  ** An i/o trap could occur at the same time as mf / divmmc cause; always check this bit in nmi isr if important
 
 
A useful NEXTREG 2, 8 will trigger the NextZXOS debugger status page, a hardware breakpoint.

Latest revision as of 17:04, 13 October 2025

Number TBRegisterNumber::$02
Readable TBRegisterReadable::Yes
Writable TBRegisterWritable::Yes
Short Description ShortDesc::Identifies type of last reset. Can be written to force reset.

Read:

 bit 7 = 1 if the reset signal to the expansion bus and esp is asserted
 bits 6:5 = Reserved
 bit 4 = 1 if multiface nmi was generated by an i/o trap (experimental, see nextreg 0xda)
 bit 3 = 1 if multiface nmi was generated by this nextreg
 bit 2 = 1 if divmmc nmi was generated by this nextreg
 bit 1 = 1 if the last reset was a hard reset
 bit 0 = 1 if the last reset was a soft reset
 * Only one of bits 1:0 will be set

Write:

 bit 7 = Assert and hold reset to the expansion bus and the esp wifi (hard reset = 0)
 bits 6:5 = Reserved must be zero
 bit 4 = Clear i/o trap (write zero to clear) (experimental) **
 bit 3 = Generate multiface nmi (write zero to clear) **
 bit 2 = Generate divmmc nmi (write zero to clear) **
 bit 1 = Generate a hard reset (reboot) *
 bit 0 = Generate a soft reset *
 * Hard reset has precedence
 ** These signals are ignored if the multiface, divmmc, dma or external nmi master is active
 ** Copper cannot clear these bits
 ** An i/o trap could occur at the same time as mf / divmmc cause; always check this bit in nmi isr if important


A useful NEXTREG 2, 8 will trigger the NextZXOS debugger status page, a hardware breakpoint.