Epson S1C63558 - Manual (Page 80)

70 EPSON S1C63558 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Programmable Timer)
4.10.7 Transfer rate setting for serial interface
The signal that is made from underflows of timer 1 by dividing them in 1/2, can be used as the clock
source for the serial interface.
The programmable timer outputs the clock to the serial interface by setting timer 1 into RUN state
(PTRUN = "1"). It is not necessary to control with the PTOUT register.
PTRUN1
Timer 1 underflow
Source clock for serial I/F
Fig. 4.10.7.1 Synchronous clock of serial interface
A setting value for the RLD1X register according to a transfer rate is calculated by the following expres-
sion:
RLD1X = fosc / (32
∗
bps
∗
division ratio of the prescaler) - 1
fosc : Oscillation frequency (OSC1/OSC3)
bps : Transfer rate
(00H can be set to RLD1X)
Be aware that the maximum clock frequency for the serial interface is limited to 1 MHz when OSC3 is
used as the clock source.