
NUC126
Aug. 08, 2018
Page
738
of 943
Rev 1.03
NUC12
6 S
E
RI
E
S
T
E
CH
NI
CA
L R
E
F
E
RE
NCE
MA
NUA
L
Divider
by 2
0
1
Divider
by 2
f
REF_CLK
f
SAMP_CLK
11
10
01
00
Divide by
1
f
PROT_CLK
f
DIV_CLK
f
SCLK
f
REF_CLK2
PTCLKSEL
(USCI_BRGEN[1])
SPCLKSEL
(USCI_BRGEN[3:2])
Figure 6.19-9 Basic Clock Divider Counter
Timing Measurement Counter
The timing measurement counter is used for time interval measurement and is enabled by TMCNTEN
(USCI_BRGEN [4]) = 1. When TMCNTSRC (USCI_BRGEN [5]) is set to 1, the timer works on
f
DIV_CLK
,
otherwise, the timer works independently from
f
PROT_CLK
. Therefore, any serial data reception or
transmission can continue while the timer is performing timing measurements. The timer counts the
length of protocol-related signals with f
PROT_CLK
or f
DIV_CLK
. It stops counting when it reaches the user-
specified value.
Divider
by 2
0
1
f
REF
_
CLK
PTCTLSEL
(USCI_BRGEN[1])
Up-Counter
f
PROT_CLK
Protocol
Relation
Definition
Clear
0
1
f
DIV_CLK
FUNMODE
(USCI_CTL [2:0])
TMCNTSRC
(USCI_BRGEN[5])
TMCNTEN
(USCI_BRGEN[4])
Figure 6.19-10 Block of Timing Measurement Counter
The timing measurement counter is used to perform time-out function or auto-baud rate mechanism.
Its functionality depends on the selected protocol as shown below.
UART: The timing measurement counter is used in auto baud rate detection.
SPI: The timing measurement counter is used for counting the slave time-out period.
I
2
C: The timing measurement counter indicates time-out clock cycle.
Sample Time Counter
A sample time counter associated to the protocol related counter defining protocol specific timings,
such shift control signals or bit timings, based on the input frequency
f
SAMP_CLK
. The sample time