sae81c80a Infineon Technologies Corporation, sae81c80a Datasheet - Page 11

• Manufacturer Part Number: sae81c80a
• Description: Cmos Dual-port Ram
• Manufacturer: Infineon Technologies Corporation

Only for the registers of timers 1 and 2
Bit 1-3: These are used together with bit 0 for switching the watchdog mode ON and
Only for the register of timer 3
Bit 1-2: Reserved (should always be 0 for correct operation).
Bit 3:
Watchdog Mode
For timers 1 and 2 a special mode was implemented which can be used to monitor the
two processors. In this mode there is a control register (CR) for each timer (see table 1
for addresses). The watchdog mode is set by loading the TMR with the value
101X1111
works similarly to the auto-reload mode, but neither the reload register nor the TMR can
be altered.
In the watchdog mode, the timer can only be restarted (and the output pulse suppressed)
if the values 055
between these two write operations is random, but the sequence must be completed
before the timer has run down, i.e. the output pulse is generated. No value may be
written into either the TMR or CR between the two write operations, otherwise the
sequence has to be started again.
To reset the timer to the normal mode, first the value 055
then the value 010X0000
too, if any other value is written into either of the two registers during the sequence, the
entire operation has to be started again. The time between the accesses is random.
The timer operation in watchdog mode is illustrated in the appendix in an 8051 example
program.
Note: The relevant bits for changing the timer state to watchdog mode are bit 0 - bit 3;
Semiconductor Group
the shown pattern is the only one, which makes sense for this mode.
OFF.
Switches all three timers to test mode, i.e. only the upper twelve bits are used
to generate the output signal (reset state = 0).
B
, the polarity of the output signal being freely selectable with bit 4. This mode
H
and 0AA
B
H
into the TMR, and finally the value 0AA
are successively written into the control register. The time
11
H
has to be written into the CR,
H
into the CR. Here,
SAE 81C80 A