TMPM330 - Keil

Baud Rate Generator
Under development
TMPM330 (rev 0.4) 9-10
TMPM330
The baud rate generator generates transmit and receive clocks to determine the serial
channel transfer rate.
The baud rate generator uses either the φT1, φT4, φT16 or φT64 clock supplied from the
7-bit prescaler. This input clock selection is made by setting the baud rate generator control
register, SC0BRCR .
The baud rate generator contains built-in dividers for divide by 1, N + m/16 (N=2~15,
m=0~15), and 16. The division is performed according to the settings of the baud rate
generator control registers SC0BRCR and SC0BRADD
to determine the resulting transfer rate.
• UART mode
1) If SC0BRCR = 0,
The setting of SC0BRADD is ignored and the counter is divided by N
where N is the value set to SC0BRCR . (N = 1 to 16).
2) If SC0BRCR = 1,
The N + (16 - K)/16 division function is enabled and the division is made by using the
values N (set in SC0BRCR ) and K (set in SC0BRADD). (N = 2
to 15, K = 1 to 15)
• I/O interface mode
(Note) For the N values of 1 and 16, the above N+(16-K)/16 division function is
inhibited. So, be sure to set SC0BRCR to “0.”
The N + (16 - K)/16 division function cannot be used in the I/O interface mode. Be sure to
divide by N, by setting SC0BRCR to “0”.
• Baud rate calculation to use the baud rate generator:
1) UART mode
Baud rate =
Baud rated generator input clock
Frequency divided by the divide ratio
The highest baud rate out of the baud rate generator is 1.0Mbps when φT1 is 16 MHz.
The fsys frequency, which is independent of the baud rate generator, can be used as
the serial clock. In this case, the highest baud rate will be 2.0 Mbps when fsys is 32
MHz.
2) I/O interface mode
Baud rated generator input clock
Baud rate =
/2
Frequency divided by the divide ratio
The highest baud rate will be generated when φT1 is 16 MHz. The divide ratio can be
set to 1 if double buffer is used and the resulting output baud rate will be 8 Mbps. (If
double buffering is not used, the highest baud rate will be 4.0 Mbps applying the divide
ratio of “2”).
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Serial Channel (SIO)