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CHAPTER 15 SERIAL INTERFACE CHANNEL 1
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(b) Busy & strobe control option
Strobe control is to synchronize data transmission/reception between the master device and a slave
device. The master device outputs a strobe signal from the STB/P23 pin on completion of transmission/
reception of 8-bit data. This strobe signal informs the slave device of the data transmission/reception
completion timing of the master device. Therefore, synchronization can be established even if bit
slippage occurs due to noise carried on the serial clock, keeping bit slippage from affecting transmission
of the next byte.
To use the strobe control option, the following conditions must be satisfied:
Set bit 5 (ATE) of the serial operating mode register 1 (CSIM1) to 1.
Set bit 2 (STRB) of the automatic data transmit/receive control register (ADTC) to 1.
Usually, the busy control and strobe control options are simultaneously used for handshaking. In this
case, the strobe signal is output from the STB/P23 pin and the BUSY/P24 pin is sampled. While a busy
signal is input to the pin, transmission/reception can be put into a wait state.
If strobe control is not executed, the P23/STB pin can be used as a normal I/O port pin.
Figure 15-21 shows the operation timings when using the busy & strobe control option.
When the strobe control option is used, the interrupt request flag that is set on completion of
transmission/reception (CSIIF1) is set after the strobe signal has been output.
Figure 15-21. Operation Timings when Using Busy & Strobe Control Option (BUSY0 = 0)
STB
SCK1
D7
SO1
SI1
CSIIF1
D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
BUSY
TRF
Busy input clear
Busy input valid
Caution
When TRF is cleared, the SO1 pin becomes low level.
Remark
CSIIF1: Interrupt request flag
TRF: Bit 3 the automatic data transmit/receive control register (ADTC)