Sensoray 526 - Manual (Page 11)

11
To change the duty cycle steps 1-2 have to be repeated with the new preload register values.
Interrupt Timer
The interrupt timer provides a way of generating interrupts at precise time intervals in the range
between approximately 100
µ
s and 25.5 ms. The timer is an 8-bit down counter with a preload
counting a 99.852
µ
s clock. Two operation modes are available: manual restart and autorestart.
In the manual restart mode the count starts on a software command and stops when the zero
count is reached. In autorestart mode the counter automatically reloads and restarts after the
zero count is reached.
Bit [0] of the Interrupt Status Register is set when the timer expires, and an interrupt is
generated if bit [0] of the Interrupt Enable Register is set to 1.
Interrupt timer expiration event can latch the output data of the counter(s), if this option is
enabled in Counter Control/Status Register(s).
Watchdog Timer
The watchdog timer has a timeout value programmable in 8 steps between 0.125 s and 16 s. If
enabled, the watchdog timer times out after a selected time interval if it is not “tagged”. Reading
the watchdog timer register “tags” it (restarts the count).
The watchdog timer generates a signal that controls a set of 2 solid-state relays (one normally
open, one normally closed) (Fig.3). Inserting a shunt in position 1-2 of jumper J6 selects a
normally open relay, inserting it in position 2-3 selects a normally closed relay.
WDT0
CONTROL
POLARITY
1
2
3
J6
WDT1
.
.
.
Fig.3. Watchdog timer output circuit.
For additional flexibility the operating mode of the watchdog timer is controlled by 2 bits of the
Watchdog Timer Control register and 2 jumpers.