TMP91C824
91C824-127
2008-02-20
•
Integer divider (N divider)
For example, when the source clock frequency (fc)
=
12.288 MHz, the input clock
frequency
=
φ
T2 (fc/16), the frequency divider N (BR0CR<BR0S3:0>)
=
5, and
BR0CR<BR0ADDE>
=
0, the baud rate in UART mode is as follows:
*
Clock state
System clock:
High frequency (fc)
Clock gear:
1 (fc)
Prescaler clock: System clock
Baud
rate
=
÷
16
=
12.288
×
10
6
÷
16
÷
5
÷
16
=
9600 (bps)
Note: The N
+
(16
−
K)/16 division function is disabled and setting
BR0ADD<BR0K3:0> is invalid.
•
N
+
(16
−
K)/16 divider (UART mode only)
Accordingly, when the source clock frequency (fc)
=
4.8 MHz, the input clock
frequency
=
φ
T0, the frequency divider N (BR0CR<BR0S3:0>)
=
7, K
(BR0ADD<BR0K3:0>)
=
3, and BR0CR <BR0ADDE>
=
1, the baud rate in UART
mode is as follows:
*
Clock state
System clock:
High frequency (fc)
Clock gear:
1 (fc)
Prescaler clock: System clock
Baud
rate
=
÷
16
=
4.8
×
10
6
÷
4
÷
(7
+
13/16)
÷
16
=
9600 (bps)
Table 3.9.3 show examples of UART mode transfer rates.
Additionally, the external clock input is available in the serial clock (Serial
channels 0, 1). The method for calculating the baud rate is explained below:
•
In UART mode
Baud rate
=
External clock input frequency
÷
16
It is necessary to satisfy (External clock input cycle)
≥
4/fc
•
In I/O interface mode
Baud rate
=
External clock input frequency
It is necessary to satisfy (External clock input cycle)
≥
16/fc
fc/16
5
fc/4
7
+
(16 – 3)/16