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NUC126
Aug. 08, 2018
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6.19.4.4 Protocol Control and Status
The protocol-related control and status information are located in the protocol control register
USCI_PROTCTL and in the protocol status register USCI_PROTSTS. These registers are shared
between the available protocols. As a consequence, the meaning of the bit positions in these registers
is different within the
protocols. Refer to each protocol’s relative register for detail information.
6.19.4.5 Protocol-Relative Clock Generator
The USCI controller contains a protocol-relative clock generator and it is controlled by register
USCI_BRGEN. It is reset when the USCI_BRGEN register is written. The structured of protocol-
relative clock generator is shown in Figure 6.19-8.
Protocol
Related
Counter
Output
Configration
RCLKSEL
(USCI_BRGEN[
0]
1'b0
f
PCLK
f
REF_C
LK
Enable
Protocol
Related Clock
f
SAMP_CL
K
f
DS_CNT
0
1
Protocol
Processor Unit
Note:
Refer the
Basic Clock Divider Counter
section to get the
f
SAMP_CLK
Figure 6.19-8 Protocol-Relative Clock Generator
The protocol related counter contains basic clock divider counter and timing measurement counter. It
is based on a divider stages, providing the frequencies needed for the different protocols. It contains:
The basic clock divider counter provides the protocol relative clock signal and other
protocol-related signals (
f
SAMP_CLK
and
f
DS_CLK
).
The timing measurement counter for time interval measurement, e.g. baud rate detection
on UART protocol.
The output signals of protocol relative clock generator can be made available on pins (e.g
USCIx_CLK for SPI).
Basic Clock Divider Counter
The basic clock divider counter is used for an integer division delivering
f
REF_CLK2
, f
REF_CLK
, f
DIV_CLK
,
f
SCLK
,
and
f
SAMP_CLK
. The frequencies of this divider are controlled by PTCLKSEL (USCI_BRGEN [1]),
CLKDIV (USCI_BRGEN [25:16]), SPCLKSEL (USCI_BRGEN [3:2]).
The basic clock divider counter is used to generate the relative protocol timing signals.
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