Chapter 13
Serial Interface 2
Operation XIII - 11
13.3 Operation
13.3.1 Serial Interface 2 Operation
Serial interface 2 is used as clock synchronous and full duplex UART serial interface.
13.3.2 Clock Synchronous Serial Interface
■ Activation Factors for Communication
Table: 13.3.1 shows activation factors for communication. In the case of master communication, a transfer clock
is generated by setting data to the transfer data buffer SC2TB or by receiving a start condition. Signal input from
the SBT2 pin is masked inside serial interface to prevent operating errors by noise, except during communica-
tion.This mask is automatically released by setting data to SC2TB (access to the SC2TB register) or feeding a
start condition to the data input pin. Therefore, in the case of slave communication, set data to SC2TB or input a
start condition before feeding external clock.
However, the external clock should be fed after more than 3.5 transfer clock intervals since data is set in SC2TB.
This wait time is necessary to load data from SC2TB into the internal shift register.
Table:13.3.1 Activation Factor for Synchronous Serial Interface
■ Transmission Data Buffer
The transmission data buffer SC2TB is a spare buffer that stores data to be loaded into the transmission shift reg-
ister. Set the data to be transmitted in the transmission data buffer SC2TB; then, data is automatically loaded into
the internal shift register. 3.5 transfer clock cycles are required for loading data. If data is set in SC2TB again dur-
ing data loading, data may not be properly set. Whether data is under loading or not can be determined by moni-
toring the transmission buffer empty flag SC2TEMP of SC2STR.
When data is set in SC2TB, the SC2TEMP flag is set to “1”, and when data loading is completed, the flag is auto-
matically cleared to “0”.
Activation factor
Transmission Reception
Master communication Set transmission data
Set dummy data
Input start condition
Slave communication
Input clock after transmission data is set.
Input clock after dummy data is set.
Input clock after start condition is input.
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