
TMS370Cx9x
8-BIT MICROCONTROLLER
SPNS036B –  JANUARY 1996 – REVISED FEBRUARY 1997
23
POST OFFICE BOX 1443 
 HOUSTON, TEXAS 77251–1443
timer 1 module (continued)
The TMS370Cx9x device includes a 24-bit watchdog (WD) timer, contained in the T1 module, which can be
software programmed as an event counter, pulse accumulator, or interval timer if the WD function is not used.
The WD function is to monitor software and hardware operation and implement a system reset when the WD
counter is not serviced properly (WD counter overflow or WD counter is reinitialized by an incorrect value). The
WD can be configured as one of the three mask options: standard WD, hard WD, or simple counter.
Standard watchdog configuration for EPROM and mask-ROM devices (see Figure 8)
–
Watchdog mode
–
Ten different WD overflow rates ranging from 6.55 ms to 3.35 s at 5-MHz SYSCLK
–
A WD reset key (WDRST) register is used to clear the watchdog counter (WDCNTR) when a correct
value is written.
–
Generates a system reset if an incorrect value is written to the WD reset key or if the counter
overflows
–
A WD overflow flag (WD OVRFL INT FLAG) bit that indicates whether the WD timer initiated a
system reset
–
Non-watchdog mode
–
Watchdog timer can be configured as an event counter, pulse accumulator, or an interval timer
16-Bit
Watchdog Counter
Reset
Prescaler
Clock
Watchdog Reset Key
WD OVRFL
TAP SEL
WD OVRFL
RST ENA
System Reset
T1CTL1.7
WDRST.7-0
WDCNTR.15-0
T1CTL2.7
T1CTL2.5
WD OVRFL
INT ENA
Interrupt
T1CTL2.6
WD OVRFL
INT FLAG
Figure 8. Standard Watchdog