Programming Notes - Epson S1C88650 Technical Manual

5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Serial Interface)

5.8.10 Programming notes

(1) Be sure to initialize the serial interface mode in
the transmitting/receiving disable status (TXEN
= RXEN = "0").
(2) Do not perform double trigger (writing "1") to
TXTRG (RXTRG) when the serial interface is in the
transmitting (receiving) operation. Furthermore, do
not execute the SLP instruction. (When executing
the SLP instruction, set TXEN = RXEN = "0".)
(3) In the clock synchronous mode, since one clock
_________
line (SCLK) is shared for both transmitting and
receiving, transmitting and receiving cannot be
performed simultaneously. (Half duplex only is
possible in clock synchronous mode.)
Consequently, be sure not to write "1" to
RXTRG (TXTRG) when TXTRG (RXTRG) is "1".
(4) When a parity error or flaming error is generated
during receiving in the asynchronous mode, the
receiving error interrupt factor flag FSERR is set
to "1" prior to the receiving complete interrupt
factor flag FSREC for the time indicated in Table
5.8.10.1. Consequently, when an error is generated,
you should reset the receiving complete interrupt
factor flag FSREC to "0" by providing a wait time in
error processing routines and similar routines.
When an overrun error is generated, the receiving
complete interrupt factor flag FSREC is not set to "1"
and a receiving complete interrupt is not generated.
Table 5.8.10.1 Time difference between FSERR
and FSREC on error generation
Clock source
f / n
OSC3
Programmable timer
(5) When the demultiplied signal of the OSC3
oscillation circuit is made the clock source, it is
necessary to turn the OSC3 oscillation ON, prior to
using the serial interface.
A time interval of several msec to several 10 msec,
from the turning ON of the OSC3 oscillation
circuit to until the oscillation stabilizes, is neces-
sary, due to the oscillation element that is used.
Consequently, you should allow an adequate
waiting time after turning ON of the OSC3
oscillation, before starting transmitting/receiving
of serial interface. (The oscillation start time will
vary somewhat depending on the oscillator and on
the externally attached parts. Refer to the
oscillation start time example indicated in Chapter
8, "ELECTRICAL CHARACTERISTICS".)
At initial reset, the OSC3 oscillation circuit is set to
ON status.
80
Time difference
1/2 cycles of f / n
OSC3
1 cycle of timer 1 underflow
EPSON
S1C88650 TECHNICAL MANUAL