Datasheet

SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
658
33.7.1.3 Receiver Clock Management
The receiver clock is generated from the transmitter clock or the divider clock or an external clock scanned on the
RK I/O pad. The Receive Clock is selected by the CKS field in SSC_RCMR (Receive Clock Mode Register).
Receive Clocks can be inverted independently by the CKI bits in SSC_RCMR.
The receiver can also drive the RK I/O pad continuously or be limited to the actual data transfer. The clock output
is configured by the SSC_RCMR. The Receive Clock Inversion (CKI) bits have no effect on the clock outputs.
Programming the RCMR to select RK pin (CKS field) and at the same time Continuous Receive Clock (CKO field)
can lead to unpredictable results.
Figure 33-8. Receiver Clock Management
33.7.1.4 Serial Clock Ratio Considerations
The Transmitter and the Receiver can be programmed to operate with the clock signals provided on either the TK
or RK pins. This allows the SSC to support many slave-mode data transfers. In this case, the maximum clock
speed allowed on the RK pin is:
 Master Clock divided by 2 if Receiver Frame Synchro is input
 Master Clock divided by 3 if Receiver Frame Synchro is output
In addition, the maximum clock speed allowed on the TK pin is:
 Master Clock divided by 6 if Transmit Frame Synchro is input
 Master Clock divided by 2 if Transmit Frame Synchro is output
33.7.2 Transmitter Operations
A transmitted frame is triggered by a start event and can be followed by synchronization data before data
transmission.
The start event is configured by setting the Transmit Clock Mode Register (SSC_TCMR). See “Start” on page 660.
The frame synchronization is configured setting the Transmit Frame Mode Register (SSC_TFMR). See “Frame
Sync” on page 662.
To transmit data, the transmitter uses a shift register clocked by the transmitter clock signal and the start mode
selected in the SSC_TCMR. Data is written by the application to the SSC_THR then transferred to the shift register
according to the data format selected.
RK (pin)
Transmitter
Clock
Divider
Clock
CKS
CKO
Data Transfer
CKI
CKG
Receiver
Clock
Clock
Output
MUX
Tri-state
Controller
Tri-state
Controller
INV
MUX