Next Reset Register

From SpecNext official Wiki
Jump to: navigation, search
Number $02
Readable Yes
Writable Yes
Short Description Identifies type of last reset. Can be written to force reset.

Read:

 bit 7 = Indicates the reset signal to the expansion bus and esp is asserted
 bits 6:2 = Reserved
 bit 1 = Indicates the last reset was a hard reset
 bit 0 = Indicates 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 6:4 = Reserved, must be 0
 bit 3 = Trigger NMI debugger on NextZXOS 
 bit 2 = Must be 0 
 bit 1 = Generate a hard reset (reboot)
 bit 0 = Generate a soft reset
 * Hard reset has precedence

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