OXCF950_06 Datasheet, PDF (46/66 Pages) Oxford Semiconductor – low cost asynchronous 16-bit PC card or Compact Flash UART device

OXFORD SEMICONDUCTOR, INC.
OXCF950 rev B DATA SHEET
Reading TCR will always return the last value that was
written to it irrespective of mode of operation.
Clock
Frequency
(MHz)
1.8432
7.3728
14.7456
18.432
32.000
33.000
40.000
50.000
60.000*
CPR value
0x08 (1.000)
0x20(4.000)
0x40 (8.000)
0x50 (10.000)
0x8B(17.375)
0x8F (17.875)
0xAE (21.750)
0xD9 (27.125)
0xFF (31.875)
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
(%)
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.
6.10.5 TTL Clock Module
Using a TTL module for the system clock simply requires
the module to be supplied with +3V3 power and GND
connections. The clock output can then be connected
directly to XTLI. XTLO should be left unconnected. Note
that the XTLI input on the OXCF950 is not 5V tolerant.
DS-0027 Feb 06
External—Free Release
Page 46 of 66