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= | |Number=$02 | ||
|Readable=Yes | |Readable=Yes | ||
|Writable=Yes | |Writable=Yes | ||
|ShortDesc=Identifies type of last reset. Can be written to force reset. | |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. | |||
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.