COP87L84FH NSC [National Semiconductor], COP87L84FH Datasheet - Page 21

• Manufacturer Part Number: COP87L84FH
• Description: 8-Bit CMOS OTP Microcontrollers with 16k Memory,
• Manufacturer: NSC [National Semiconductor]

Baud Clock Generation
Prescaler
TABLE 3. Prescaler Factors
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
NO CLOCK
Prescaler
Factor
FIGURE 15. USART BAUD Clock Divisor Registers
10.5
11.5
12.5
13.5
14.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
FIGURE 14. USART BAUD Clock Generation
(Continued)
21
As an example, considering the Asynchronous Mode and a
CKI clock of 4.608 MHz, the prescaler factor selected is:
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
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.
134.5 (134.58)
110 (110.03)
(1.8432 MHz Prescaler Output)
TABLE 4. Baud Rate Divisors
Prescaler
19200
38400
Baud
Select
1200
1800
2400
3600
4800
7200
9600
11110
11111
Rate
150
300
600
4.608/1.8432 = 2.5
DS101135-19
Divisor − 1 (N-1)
Baud Rate
Prescaler
Factor
1046
855
767
383
191
15.5
95
63
47
31
23
15
11
5
2
16
DS101135-18
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