R8C/1A Group, R8C/1B Group
16. Clock Synchronous Serial Interface
Rev.1.30
Dec 08, 2006
Page 197 of 315
REJ09B0252-0130
16.2.7
SCS Pin Control and Arbitration
When setting the SSUMS bit in the SSMR2 register to 1 (4-wire bus communication mode).and the CSS1 bit in
the SSMR2 register to 1 (functions as SCS output pin), set the MSS bit in the SSCRH register to 1 (operates as
the master device) and check the arbitration of the SCS pin before starting serial transfer. If clock synchronous
serial I/O with chip select detects that the synchronized internal SCS signal is held “L” in this period, the CE bit
in the SSSR register is set to 1 (conflict error) and the MSS bit is automatically set to 0 (operates as a slave
device).
Figure 16.21 shows the Arbitration Check Timing.
Future transmit operations are not performed while the CE bit is set to 1. Set the CE bit to 0 (no conflict error)
before starting transmission .
Figure 16.21
Arbitration Check Timing
Data write to
SSTDR register
Maximum time of SCS internal
synchronization
During arbitration detection
High-impedance
SCS input
Internal SCS
(synchronization)
MSS bit in
SSCRH register
Transfer start
CE
SCS output
0
1
