OXCB950
OXFORD SEMICONDUCTOR LTD.
values in bits-per-second (bps) that are obtained if the
divisor latch = 0x01 and the Prescaler is set to 1.
Use of the TCR does not require the device to be in 650 or
950 mode although only drivers that have been written to
take advantage of the 950 mode features will be able to
access this register. Writing 0x01 to the TCR will not switch
the device into 1x isochronous mode, this is explained in
the following section. (TCR has no effect in isochronous
mode). If 0x01, 0x10 or 0x11 is written to TCR the device
will operate in 16x mode.
The OXCB950 has the facility to operate at baud-rates up
to 15 Mbps in normal mode.
Table 26 indicates how the value in the register
corresponds to the number of clock cycles per bit. TCR[3:0]
is used to program the clock. TCR[7:4] are unused and will
return “0000” if read.
Reading TCR will always return the last value that was
written to it irrespective of mode of operation.
TCR[3:0]
Clock cycles per bit
0000 to 0011
0100 to 1111
16
4-15
Table 20: TCR Sample Clock Configuration
Clock
Frequency
(MHz)
CPR value
Effective
crystal
frequency
1.8432
1.8432
1.8432
1.8432
1.8417
1.8462
1.8391
1.8433
1.8824
Error from
1.8432MHz
(%)
Max. Baud rate
with CPR = 1,
TCR = 16
115,200
Max. Baud rate
with CPR = 1,
TCR = 4
1.8432
7.3728
14.7456
18.432
32.000
33.000
40.000
50.000
60.000
0x08 (1)
0x20 (4)
0.00
460,800
0.00
460,800
1,843,200
3,686,400
4,608,000
8,000,000
8,250,000
10,000,000
12,500,000
15,000,000
0x40 (8)
0.00
921,600
0x50 (10)
0.00
1,152,000
2,000,000
2,062,500
2,500,000
3,125,000
3,750,000
0x8B (17.375)
0x8F (17.875)
0xAE (21.75)
0xD9 (27.125)
0xFF (31.875)
0.08
0.16
0.22
0.01
2.13
Table 21: Example clock options and their associated maximum baud rates
Sampling TCR
System Clock (MHz)
Clock Value
1.8432
7.372
14.7456
18.432
32
2.00M
40
50
60
3.75M
4.00M
16
15
14
13
12
11
10
9
0x00 115,200
0x0F 122,880
0x0E 131,657
0x0D 141,785
0x0C 153,600
0x0B 167,564
0x0A 184,320
0x09 204,800
0x08 230,400
460,750 921,600
1.152M
2.50M 3.125M
491,467 983,040 1,228,800 2,133,333 2,666,667 3,333,333
526,571 1,053,257 1,316,571 2,285,714 2,857,143 3,571,429 4,285,714
567,077 1,134,277 1,417,846 2,461,538 3,076,923 3,846,154 4,615,384
614,333 1,228,800 1,536,000 2,666,667 3,333,333 4,166,667
670,182 1,340,509 1,675,636 2,909,091 3,636,364 4,545,455 5,454545
737,200 1,474,560 1,843,200 3.20M 4.00M 5.00M 6.00M
819,111 1,638,400 2,048,000 3,555,556 4,444,444 5,555,556 6,666,667
921,500 1,843,200 2,304,000 4.00M 5.00M 6.25M 7.50M
5.00M
8
7
0x07 263,314 1,053,143 2,106,514 2,633,143 4,571,429 5,714,286 7,142,857 8,571428
0x06 307,200 1,228,667 2,457,600 3,072,000 5,333,333 6,666,667 8,333,333 10.00M
0x05 368,640 1,474,400 2,949,120 3,686,400
0x04 460,800 1,843,000 3,686,400 4,608,000
6
5
6.40M
8.00M 10.00M 12.00M
4
8.00M 10.00M 12.50M 15.00M
Table 22: Maximum Baud Rates Available at all ‘TCR’ Sampling Clock Values
DS-0033 Sep 05
External-Free Release
Page 45
OXFORD [ OXFORD SEMICONDUCTOR ]
