252
Simultaneous transmitting and receiving:
The procedure for simultaneously transmitting and
receiving data is as follows.
(1) Set SO1, SI1, and SCK1 all to 1 in PMR2 to designate the SO1, SI1, and SCK1 functions.
(2) Clear SNC1 in SCR1 to 0, clear or set SNC0 to 0 or 1, and clear MRKON to 0, to select 8-bit
synchronous mode or 16-bit synchronous mode, and select the serial clock with bits CKS3 to
CKS0. When data is written to SCR1 with MRKON in SCR1 cleared to 0, the internal state of
SCI1 is initialized.
(3) Write the transfer data to SDRL/SDRU.
8-bit transfer mode: SDRL
16-bit transfer mode: Upper byte to SDRU, lower byte to SDRL
(4) When STF is set to 1 in SCSR1, SCI1 starts operating and transmit data is output from the
SO1, or receive data is input from the SI1.
(5) After transmission/reception is completed, IRRS1 is set to 1 in IRR1.
(6) Read the transfer data from SDRL/SDRU.
8-bit transfer mode: SDRL
16-bit transfer mode: Upper byte from SDRU, lower byte from SDRL
When an internal clock is used, the serial clock is output from the SCK
1
simultaneously with
transmit data output. When transmission ends, the serial clock is not output until the start flag is
next set to 1. During this interval, the SO
1
continuously outputs the last bit of the previous data.
While transmission is halted, the output value of the SO
1
pin can be changed by means of the SOL
bit in SCSR1.
10.2.4
Interrupt Source
SCI1 has one interrupt source: transfer completion.
When SCI1 completes transfer, IRRS1 is set to 1 in IRR1. The SCI1 interrupt source can be
enabled or disabled by the IENS1 bit in IENR1.
For details, see 3.3, Interrupts.