AT91SAM7S32-AI ATMEL [ATMEL Corporation], AT91SAM7S32-AI Datasheet - Page 313

• Manufacturer Part Number: AT91SAM7S32-AI
• Description: AT91 ARM Thumb-based Microcontrollers
• Manufacturer: ATMEL [ATMEL Corporation]

Clock Divider
Transmitter Clock
Management
6071A–ATARM–28-Oct-04
Figure 133. Divided Clock Block diagram
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 divi-
sion 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 or greater to 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 if the
DIV value is even or odd.
Figure 134. Divided Clock Generation
Table 71. Bit Rate
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 Inver-
sion (CKI) bits have no effect on the clock outputs. Programming the TCMR register to select
TK pin (CKS field) and at the same time Continuous Transmit Clock (CKO field) might lead to
unpredictable results.
Maximum
MCK / 2
Divided Clock
Divided Clock
Master Clock
Master Clock
DIV = 3
DIV = 1
MCK
/ 2
Divided Clock Frequency = MCK/2
Divided Clock Frequency = MCK/6
Clock Divider
AT91SAM7S32 Preliminary
12-bit Counter
Minimum
MCK / 8190
SSC_CMR
Divided Clock
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