PC87591L-N05 Datasheet, PDF (152/401 Pages) National Semiconductor (TI) – LPC Mobile Embedded Controller

4.0 Embedded Controller Modules (Continued)
Table 20. Pre-Scaler Factors
Pre-Scaler Select
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
Pre-Scaler Factor
NO CLOCK
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
Pre-Scaler Select
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
Pre-Scaler Factor
8.5
9
9.5
10
10.5
11
11.5
12
12.5
13
13.5
14
14.5
15
15.5
16
where:
• BR is the baud rate
• SYS_CLK is the system clock
• N is the value of the baud rate divisor + 1
• P is the pre-scaler divide factor selected by the value in the PSR register
The divide by 16 operation is performed because in Asynchronous mode, the input frequency to the USART is 16 times the
baud rate. In Synchronous mode, the input clock to the USART is equal to the baud rate.
Interrupts
The USART is capable of generating interrupts on one of the following conditions:
• Receive Buffer Full
• Receive Error
• Transmit Buffer Empty
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