COP87L88FH Datasheet, PDF (21/45 Pages) National Semiconductor (TI) – 8-Bit CMOS OTP Microcontrollers with 16k Memory,

Baud Clock Generation (Continued)
FIGURE 14. USART BAUD Clock Generation
DS101135-18
DS101135-19
FIGURE 15. USART BAUD Clock Divisor Registers
TABLE 3. Prescaler Factors
Prescaler
Select
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
Prescaler
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
8.5
9
9.5
10
10.5
11
11.5
12
12.5
13
13.5
14
14.5
15
Prescaler
Select
11110
11111
Prescaler
Factor
15.5
16
TABLE 4. Baud Rate Divisors
(1.8432 MHz Prescaler Output)
Baud
Rate
110 (110.03)
134.5 (134.58)
150
300
600
1200
1800
2400
3600
4800
7200
9600
19200
38400
Baud Rate
Divisor − 1 (N-1)
1046
855
767
383
191
95
63
47
31
23
15
11
5
2
The entries in Table 4 assume a prescaler output of 1.8432
MHz. In the asynchronous mode the baud rate could be as high
as 625k.
As an example, considering the Asynchronous Mode and a
CKI clock of 4.608 MHz, the prescaler factor selected is:
4.608/1.8432 = 2.5
The 2.5 entry is available in Table 3. The 1.8432 MHz pres-
caler output is then used with proper Baud Rate Divisor
Table 4 to obtain different baud rates. For a baud rate of
19200 e.g., the entry in Table 4 is 5.
N − 1 = 5 (N − 1 is the value from Table 4)
N = 6 (N is the Baud Rate Divisor)
Baud Rate = 1.8432 MHz/(16 x 6) = 19200
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