Toshiba PROSEC T3 User Manual page 59

(5) Operation
PI312 counts the pulses phase A and phase B. Phase A is counting up (increase),
and phase B is counting down (decrease). When both phase A and phase B come ON
simultaneously, counting is not executed.
In the normal count mode, PI312 counts at the rising edge of the pulse. On the other
hand, in the precision count mode, PI312 counts at both rising and falling edges of the
pulse. Therefore the count value becomes double in the precision count mode.
This mode function is enabled while both phase G and soft-gate are ON. (even when
the either is OFF, counting is not stopped)
The count value can be changed by directly writing a data into the buffer memory.
Also,
the count value is cleared to 0 by hardware at the following timing.
a) At the moment of both phase G and soft-gate come ON
b) At the moment of phase M comes ON while EXT is ON (100 ms or more of EXT
ON state is necessary before phase M comes ON)
When the count value is increased by 1 in the upper limit value (16777215), it is reset
to 0. When the count value is decreased by 1 in the lower limit value (0), it is reset to
the upper limit value (16777215).
When the output-enable bit in the command register (YW) is ON, the hardware
comparison outputs (S1 and S2) are enabled. In this condition, when the count value
is greater than the set-point-1, S1 comes ON. And when the count value is smaller
than the set-point-2, S2 comes ON.
When the interrupt-enable bit in the command register (YW) is ON, PI312's interrupt
function is enabled. In this condition, when the count value reaches the set-point-1 in
counting up or it reaches the set-point-2 in counting down, the PI312 generates
interrupt signal for the T3. Then corresponding I/O interrupt program in the T3 will be
started immediately. For details of the interrupt function, refer to section 7.
When phase G or soft-gate comes OFF, the current count value is transferred into the
hold register.
6. Function Details
57
User's Manual