CHAPTER 9 8-BIT SERIAL I/O
Table 9.3-1 Serial mode register (SMR) bits
Bit
Bit 0
SST:
Serial I/O transfer
start bit
178
•
This bit controls serial I/O transfer start and transfer enable. This bit can also be used to determine
whether transfer has completed.
•
Writing "1" to this bit when an internal shift clock is selected (CKS1, CKS0 = other than "11
clears the shift clock counter and starts data transfer.
•
Writing "1" to this bit when an external shift clock is selected (CKS1, CKS0 = "11
transfer, clears the shift clock counter, and sets serial I/O to delay for input of the external shift
clock.
•
This bit is cleared to "0" and the SIOF bit is set to "1" when transfer completes.
•
Writing "0" to this bit while transfer is in progress (SST = "1") aborts the transfer.
After halting a transfer, data must be set again to the SDR register for data output and transfer
restarted (the shift clock counter cleared) for data input.
Function
")
B
") enables data
B