240
Bit 1—Bit 0 Write Inhibit (B0WI): Bit 1 controls writing of data to bit 0 of timer control/status
register W.
Bit 1: B0WI
Description
0
Writing to bit 0 is enabled
1
Writing to bit 0 is disabled
(Initial value)
This bit is always read as 1. Data is not stored if written to this bit.
Bit 0—Watchdog Timer Reset (WRST): Bit 0 indicates that TCW has overflowed and an
internal reset signal has been generated. The internal reset signal generated by the overflow resets
the entire chip.
WRST is cleared by a reset via the
RES
pin or by a 0 write by software.
Bit 0: WRST
Description
0
[Clearing conditions]
(Initial value)
•
Reset by
RES
pin
•
When 0 is written to WRST while writing 0 to B0WI when TCSRWE = 1
1
[Setting condition]
When TCW overflows and an internal reset signal is generated
13.2.2
Timer Counter WD (TCWD)
Bit
7
6
5
4
3
2
1
0
TCWD7
TCWD6
TCWD5
TCWD4
TCWD3
TCWD2
TCWD1
TCWD0
Initial value
0
0
0
0
0
0
0
0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
TCWD is an 8-bit read/write up-counter that is incremented by an input internal clock. The
TCWD value can be read or written by the CPU at any time.
When TCWD overflows (from H'FF to H'00), an internal reset signal is generated and WRST in
TCSRWD is set to 1. Upon reset, TCWD is initialized to H'00.
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