
Watchdog Timer Hold-Off Register
Watchdog Timer Hold-Off Register
WDHOLD (WRITE ONLY) 00E1h (or 01E1h via CMOS Setup)
D7 D6 D5 D4 D3 D2 D1 D0
0 1 0 1 1 0 1 0
A watchdog timer circuit is included on the
EPM-CPU-10
board to reset the CPU or issue an NMI if
proper software execution fails or a hardware malfunction occurs. The watchdog timer is
enabled/disabled by writing to bit D0 of SCR
If the watchdog timer is enabled, software must periodically refresh the watchdog timer at a rate
faster than the timer is set to expire (1 second minimum). Writing a 5Ah to WDHOLD resets the
watchdog timeout period, preventing the CPU from being reset or generation of NMI for the next
1 second.
Special Control Register
SCR (READ/WRITE) 00E2h (or 01E2h via CMOS setup)
D7 D6 D5 D4 D3
D2
D1
D0
Reserved Reserved Reserved Reserved Reserved Reserved
JPI
Throttle
Table 21: Special Control Register Bit Assignments
Bit Mnemonic Description
D7-D2 Reserved Reserved — These bits have no function.
D1 JPI
Jumper Input — Indicates the status of jumper VS2[5-6]
JPI = 0
Jumper VS2[5-6] = Out
JPI = 1
Jumper VS2[5-6] = In
Note! This bit is a read-only bit.
D0 Throttle
Throttling Enable — Enables and disables CPU throttling.
Throttling = 0
Disable
Throttling = 1
Enable
Note! Models C & D are read write. Models B & E are set only and cleared by Reset.
EPM-CPU-10 Reference Manual
Reference – 43