3 receiver operations, 4 start – Rainbow Electronics AT91CAP9S250A User Manual
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6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
36.6.3
Receiver Operations
A received frame is triggered by a start event and can be followed by synchronization data
before data transmission.
The start event is configured setting the Receive Clock Mode Register (SSC_RCMR).
The frame synchronization is configured setting the Receive Frame Mode Register
(SSC_RFMR).
The receiver uses a shift register clocked by the receiver clock signal and the start mode
selected in the SSC_RCMR. The data is transferred from the shift register depending on the
data format selected.
When the receiver shift register is full, the SSC transfers this data in the holding register, the sta-
tus flag RXRDY is set in SSC_SR and the data can be read in the receiver holding register. If
another transfer occurs before read of the RHR register, the status flag OVERUN is set in
SSC_SR and the receiver shift register is transferred in the RHR register.
Figure 36-9. Receiver Block Diagram
36.6.4
Start
The transmitter and receiver can both be programmed to start their operations when an event
occurs, respectively in the Transmit Start Selection (START) field of SSC_TCMR and in the
Receive Start Selection (START) field of SSC_RCMR.
Under the following conditions the start event is independently programmable:
• Continuous. In this case, the transmission starts as soon as a word is written in SSC_THR
and the reception starts as soon as the Receiver is enabled.
• Synchronously with the transmitter/receiver
• On detection of a falling/rising edge on TF/RF
• On detection of a low level/high level on TF/RF
• On detection of a level change or an edge on TF/RF
Receive Shift Register
Start
Selector
SSC_RHR
SSC_RSHR
Receiver Clock
RD
SSC_RFMR.FSLEN
SSC_RFMR.DATLEN
RF
SSC_CR.RXEN
SSC_CR.RXDIS
SSC_SR.RXEN
SSC_RFMR.MSBF
SSC_RCMR.STTDLY
SSC_RFMR.DATNB
TF