![](http://datasheet.mmic.net.cn/Exar-Corporation/XR20M1280IL40-F_datasheet_100087/XR20M1280IL40-F_16.png)
FIGURE 13. BAUD RATE GENERATOR
XTAL1
XTAL2
/
-
(default)
16X or 8X or 4X
Sampling Rate Clock
to Transmitter
Prescaler
Divide by 1
Prescaler
Divide by 4
MCR Bit 7= 0
MCR Bit -7=1
Crystal
Osc
Buffer
DLL
DLM
DLD[5:0]
DLL
DLM
DLD[5:0]
16X or 8X or 4X
Sampling Rate Clock
to Receiver
DLD[7]=0
DLD[7]=1
0
1
DLD[6]
TABLE 6: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING
Required Output
Data Rate
DIVISOR FOR 16x
Clock (Decimal)
DLM PROGRAM
VALUE (HEX)
DLL PROGRAM
VALUE (HEX)
DLD PROGRAM
VALUE (HEX)
DATA ERROR
RATE (%)
400
3750
E
A6
0
2400
625
2
71
0
4800
312.5
1
38
8
0
9600
156.25
0
9C
4
0
10000
150
0
96
0
19200
78.125
0
4E
2
0
25000
60
0
3C
0
28800
52.0833
0
34
1
0.04
38400
39.0625
0
27
1
0
50000
30
0
1E
0
57600
26.0417
0
1A
0
0.08
75000
20
0
14
0
100000
15
0
F
0
115200
13.0208
0
D
0
0.16
153600
9.7656
0
9
C
0.16
200000
7.5
0
7
8
0
225000
6.6667
0
6
A
0.31
230400
6.5104
0
6
8
0.16
250000
6
0
6
0
300000
5
0
5
0
400000
3.75
0
3
C
0
460800
3.2552
0
3
4
0.16
500000
3
0
3
0
750000
2
0
2
0
921600
1.6276
0
1
A
0.16
1000000
1.5
0
1
8
0
XR20M1280
16
I2C/SPI UART WITH 128-BYTE FIFO AND INTEGRATED LEVEL SHIFTERS
REV. 1.0.0