SAM7X128_14 Datasheet, PDF (340/662 Pages) ATMEL Corporation – ARM-based Flash MCU

Furthermore, the transmitter block can generate an external clock on the TK I/O pad, and the receiver block can generate
an external clock on the RK I/O pad.
This allows the SSC to support many Master and Slave Mode data transfers.
31.6.1.1 Clock Divider
Figure 31-4. Divided Clock Block Diagram
Clock Divider
SSC_CMR
MCK
/2
12-bit Counter
Divided Clock
The Master Clock divider is determined by the 12-bit field DIV counter and comparator (so its maximal value is 4095) in
the Clock Mode Register SSC_CMR, allowing a Master Clock division by up to 8190. The Divided Clock is provided to
both the Receiver and Transmitter. When this field is programmed to 0, the Clock Divider is not used and remains
inactive.
When DIV is set to a value equal to or greater than 1, the Divided Clock has a frequency of Master Clock divided by 2
times DIV. Each level of the Divided Clock has a duration of the Master Clock multiplied by DIV. This ensures a 50% duty
cycle for the Divided Clock regardless of whether the DIV value is even or odd.
Figure 31-5.
Divided Clock Generation
Master Clock
Divided Clock
DIV = 1
Divided Clock Frequency = MCK/2
Master Clock
Divided Clock
DIV = 3
Divided Clock Frequency = MCK/6
Table 31-2.
Maximum
MCK / 2
Minimum
MCK / 8190
31.6.1.2 Transmitter Clock Management
The transmitter clock is generated from the receiver clock or the divider clock or an external clock scanned on the TK I/O
pad. The transmitter clock is selected by the CKS field in SSC_TCMR (Transmit Clock Mode Register). Transmit Clock
can be inverted independently by the CKI bits in SSC_TCMR.
The transmitter can also drive the TK I/O pad continuously or be limited to the actual data transfer. The clock output is
configured by the SSC_TCMR register. The Transmit Clock Inversion (CKI) bits have no effect on the clock outputs.
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
340