CHAPTER 14 SERIAL INTERFACE CHANNEL 1
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User’s Manual U11302EJ4V0UM
(c) Bit slippage detection function with busy signal
During automatic transmission/reception, bit slippage may take place in the serial clock of the slave
device due to the noise carried on the serial clock signal output by the master device. Unless the
strobe control option is used at this time, the bit slippage affects transmission of the next byte. In
such a case, the master device can detect the bit slippage by using the busy control option and
checking the busy signal during transmission.
The bit slippage is detected by using the busy signal as follows.
The slave outputs a busy signal after the 8th rise of the serial clock during data transmission/reception
(at this time, make the busy signal inactive within two clocks to stop the master device putting
transmission/reception into a wait state).
The master samples the busy signal in synchronization with the fall of the serial clock. If bit slippage
does not occur, the busy signal is found to be inactive after it has been sampled eight times. If the
busy signal is found to be active when it has been sampled, it is assumed that bit slippage has
occurred, and error processing is performed (by setting bit 4 (ERR) of the automatic data transmit/
receive control register (ADTC) to 1).
Figure 14-22 shows the operation timing of the bit slippage detection function using the busy signal.
Figure 14-22. Operation Timing of Bit Slippage Detection Function Using Busy Signal (BUSY0 = 1)
SCK1
D7
SO1
SI1
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
CSIIF1
CSIE1
ERR
D7
D7
No busy detection
Error interrupt request generation
Error detection
Bit slippage due to noise
(Slave side)
SCK1
(Master side)
CSIIF1: Interrupt request flag
CSIE1: Bit 7 of serial operating mode register 1 (CSIM1)
ERR:
Bit 4 of the automatic data transmit/receive control register (ADTC)
Содержание mPD780208 Subseries
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