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III PERIPHERAL BLOCK: 8-BIT PROGRAMMABLE TIMERS
S1C33210 FUNCTION PART EPSON B-III-3-7
Control of Clock Output
When outputting an underflow signal of the 8-bit programmable timer to external devices, or when supplying a clock
generated by the underflow signal to the serial interface, it is necessary to control the clock output of the timer.
Timer 0 clock output control: PTOUT0 (D2) / 8-bit timer 0 control register (0x40160)
Timer 1 clock output control: PTOUT1 (D2) / 8-bit timer 1 control register (0x40164)
Timer 2 clock output control: PTOUT2 (D2) / 8-bit timer 2 control register (0x40168)
Timer 3 clock output control: PTOUT3 (D2) / 8-bit timer 3 control register (0x4016C)
To output the underflow signal/clock, write "1" to PTOUTx. If an output pin has been set, the underflow signal is
output from that pin.
The same applies when timer 2 or 3 has been set as the clock source of the serial interface. A clock generated from the
underflow signal by dividing it by 2 is output to the serial interface through this control. The clock output is turned
off by writing "0" to PTOUTx, and the external output is fixed at "0" and the internal clock output is fixed at "1".
Figure 3.3 shows the waveforms of the output signals.
Underflow signal
Underflow signal/2
PTOUTx
External output
T8UFx pin
Clock output
Figure 3.3 8-Bit Programmable Timer Output Waveform
The underflow signal's pulse width (duration of the high period) is equal to that of the timer's input clock (prescaler's
output).
8-bit timer external output (P10–P13 ports)
1) After an initial reset (cold start), the ports (P10–P13) are set to debug signal putput ports.
2) The port (P10–P13) outputs "0" when it is set to the 8-bit timer output (timer output is off status).
3) The timer output is left as "0" when the timer output is turned on after setting the input clock and timer initial
value.
4) When an underflow occurs after starting the timer, the port outputs a pulse with the same width as the 8-bit
timer input clock pulse (prescaler's output).