XR17V258 Datasheet, PDF (32/70 Pages) Exar Corporation – 66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT

XR17V258
66MHZ PCI BUS OCTAL UART WITH POWER MANAGEMENT SUPPORT
xr
REV. 1.0.0
The closest divisor that is obtainable in the V258 can be calculated using the following formula:
ROUND( (Required Divisor - TRUNC (Required Divisor) )*16)/16 + TRUNC (Required Divisor), where
DLM = TRUNC( Required Divisor) >> 8
DLL = TRUNC (Required Divisor) & 0xFF
DLD = ROUND ( (Required Divisor-TRUNC(Required Divisor) )*16)
In the formulas above, please note that:
TRUNC (N) = Integer Part of N. For example, TRUNC (5.6) = 5.
ROUND (N) = N rounded towards the closest integer. For example, ROUND (7.3) = 7 and ROUND (9.9) = 10.
FIGURE 11. BAUD RATE GENERATOR
To Other
Channels
XTAL1
XTAL2
Crystal
Osc/
Buffer
Prescaler
Divide by 1
Prescaler
Divide by 4
DLL, DLM and DLD
Registers
MCR Bit-7=0
(default)
Fractional Baud
Rate Generator
Logic
MCR Bit-7=1
16X or 8X
Sampling
Rate Clock
to Transmitter
and Receiver
TABLE 12: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING
REQUIRED
OUTPUT DATA
RATE
DIVISOR FOR
16x Clock
(Decimal)
DIVISOR
OBTAINABLE IN
V258
DLM PROGRAM
VALUE (HEX)
DLL PROGRAM DLD PROGRAM
VALUE (HEX) VALUE (HEX))
DATA ERROR
RATE (%)
400
3750
3750
E
A6
0
0
2400
625
625
2
71
0
0
4800
312.5
312 8/16
1
38
8
0
9600
156.25
156 4/16
0
9C
4
0
10000
150
150
0
96
0
0
19200
78.125
78 2/16
0
4E
2
0
25000
60
60
0
3C
0
0
28800
52.0833
52 1/16
0
34
1
0.04
38400
39.0625
39 1/16
0
27
1
0
50000
30
30
0
1E
0
0
57600
26.0417
26 1/16
0
1A
1
0.08
75000
20
20
0
14
0
0
32