OXCF950 Datasheet, PDF (46/66 Pages) Oxford Semiconductor – Single full-duplex asynchronous channel 128-byte deep transmitter / receiver FIFO

OXFORD SEMICONDUCTOR LTD.
OXCF950 rev B DATA SHEET V 1.0
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.
Reading TCR will always return the last value that was
written to it irrespective of mode of operation.
Clock
Frequency
CPR value Effective
crystal
(MHz)
frequency
1.8432
0x08 (1.000) 1.8432
7.3728
0x20(4.000) 1.8432
14.7456
0x40 (8.000) 1.8432
18.432
32.000
0x50 (10.000) 1.8432
0x8B(17.375) 1.8417
33.000
0x8F (17.875) 1.8462
40.000
0xAE (21.750) 1.8391
50.000
0xD9 (27.125) 1.8433
60.000*
0xFF (31.875) 1.8824
Error from
1.8432MHz
(%)
0.00
0.00
0.00
0.00
0.08
0.16
0.22
0.01
2.13
Max. Baud rate
with CPR = 1,
TCR = 16
115,200
460,800
921,600
1,152,000
2,000,000
2,062,500
2,500,000
3,125,000
3,750,000
Max. Baud rate
with CPR = 1,
TCR = 4
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
Table 37: Example clock options and their associated maximum baud rates
Sampling TCR
Clock Value
16 0x00
15 0x0F
14 0x0E
13 0x0D
12 0x0C
11 0x0B
10 0x0A
9 0x09
8 0x08
7 0x07
6 0x06
5 0x05
4 0x04
1.8432
115,200
122,880
131,657
141,785
153,600
167,564
184,320
204,800
230,400
263,314
307,200
368,640
460,800
System Clock (MHz)
7.372 14.7456 18.432
32
40
50
60
460,750 921,600 1.152M 2.00M 2.50M 3.125M 3.75M
491,467 983,040 1,228,800 2,133,333 2,666,667 3,333,333 4.00M
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 5.00M
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
1,053,143 2,106,514 2,633,143 4,571,429 5,714,286 7,142,857 8,571428
1,228,667 2,457,600 3,072,000 5,333,333 6,666,667 8,333,333 10.00M
1,474,400 2,949,120 3,686,400 6.40M 8.00M 10.00M 12.00M
1,843,000 3,686,400 4,608,000 8.00M 10.00M 12.50M 15.00M
Table 38: Maximum Baud Rates Available at all ‘TCR’ Sampling Clock Values
6.10.4 Input Clock Options
A system clock must be applied to XTLI pin on the device.
The speed of this clock determines the maximum baud rate
at which the device can receive and transmit serial data.
This maximum is equal to one sixteenth of the frequency of
the system clock (Increasing to one quarter of this value if
TCR=4 is used).
The industry standard system clock for PC COM ports is
1.8432 MHz, limiting the maximum baud rate to 115.2
Kbps. The OXCF950 supports system clocks up to 60MHz
and its flexible baud rate generation hardware means that
almost any frequency can be optionally scaled down for
compatibility with standard devices.
Designers have the option of using either TTL clock
modules or crystal oscillator circuits for system clock input,
with minimal additional components. The following two
sections describe how each can be connected. Note
restrictions on the maximum clock frequency may apply
when an external EEPROM is being used. The designer
must ensure the clock frequency/64 is within the external
EEPROM’s allowed range.
Page 46