NEC Network Controller uPD98502 - Manual (Page 225)

CHAPTER 3 SYSTEM CONTROLLER
Preliminary User’s Manual S15543EJ1V0UM 225
3.6.5 DSUTIMR (DSU Elapsed Time Register)
This register indicates the elapsed time for the current Deadman’s Switch timer.
DSUTIMR is a read-only and 32-bit word-aligned register. Default is 0H.
Bits Field R/W Default Description
31:0 CRTTIM R 0 Current Deadman’s Switch timer value (Elapsed time)
example:
CRTTIM = 05F5_E100H (100 MHz) or 03F9_40AAH (66 MHz) ->1 sec
CRTTIM = 0BEB_C200H (100 MHz) or 07F2_8154H (66 MHz) -> 2 sec
CRTTIM = 11E1_A300H (100 MHz) or 0BEB_C200H (66 MHz) -> 3 sec
: : :
3.6.6 DSU register setting flow
The DSU register setting flow is described below.
1. Set the DSU’s count-up value (from 1 to 231 – 1).
The CPU will be reset if it does not clear (1 is not written to DSUCLRR) the timer within this period.
2. Enable the DSU
3. Clear the timer within the period specified in step 1 above.
For normal use, repeat step 3. To obtain the current elapsed time, read DSUTIMR.
4. Disable the DSU for shutdown.