IBM nec pd78081(a) User Manual

CLOE

PCL/P35 Pin Output

*

*

The clock output control circuit is intended for carrier output during remote controlled transmission and clock output

for supply to peripheral LSI.  Clocks selected with the timer clock select register 0 (TCL0) are output from the PCL/

P35 pin.

Follow the procedure below to output clock pulses.

 (1) Select the clock pulse output frequency (with clock pulse output disabled) with bits 0 to 3 (TCL00 to TCL03)

of TCL0.

 (2) Set the P35 output latch to 0.

 (3) Set bit 5 (PM35) of port mode register 3 to 0 (set to output mode).

 (4) Set bit 7 (CLOE) of timer clock select register 0 to 1.

When clock output enable/disable is switched, the clock output control circuit does not output pulses

with small widths (See the portions marked with * in Figure 8-1).