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TMP92CM22
2007-02-16
92CM22-146
(2) Baud rate generator
The baud rate generator is a circuit that generates transmission and receiving clocks
that determine the transfer rate of the serial channels.
The input clock to the baud rate generator, φT0, φT2, φT8, or φT32, is generated by
the 6-bit prescaler which is shared by the timers. One of these input clocks is selected
using the BR0CR<BR0CK1:0> field in the baud rate generator control register.
The baud rate generator includes a frequency divider, which divides the frequency by
1 or N + (16 − K)/16 to 16 values, determining the transfer rate.
The transfer rate is determined by the settings of BR0CR<BR0ADDE, BR0S3:0> and
BR0ADD<BR0K3:0>.
• In UART mode
(1) When BR0CR<BR0ADDE> = 0
The settings BR0ADD<BR0K3:0> are ignored. The baud rate generator divides
the selected prescaler clock by N (N = 1, 2, 3 ... 16), which is set in
BR0CR<BR0S3:0>.
(2) When BR0CR<BR0ADDE> = 1
The N + (16 – K)/16 division function is enabled. The baud rate generator
divides the selected prescaler clock by N + (16 − K)/16 using the value of N (N = 2,
3 ... 15) set in BR0CR<BR0S3:0> and the value of K (K = 1, 2, 3 ... 15) set in
BR0ADD<BR0K3:0>.
Note: If N = 1 and N = 16, the N + (16 − K)/16 division function is disabled.
Clear BR0CR<BR0ADDE> register to “0”.
• In I/O interface mode
The N + (16 − K)/16 division function is not available in I/O interface mode. Clear
BR0CR<BR0ADDE> to 0 before dividing by N.
The method for calculating the transfer rate when the baud rate generator is
used is explained below.
• UART mode
Input clock of baud rate generator
Frequency divider for baud rate generator
• I/O interface mode
Input clock of baud rate generator
Frequency divider for baud rate generator
Baud rate =
÷ 16
Baud rate =
÷ 2