OXCF950 datasheet(46/66 Pages) OXFORD

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OXCF950 rev B DATA SHEET

OXFORD SEMICONDUCTOR, INC.

Reading TCR will always return the last value that was

written to it irrespective of mode of operation.

Clock

Frequency

(MHz)

CPR value

Effective

crystal

frequency

Error from

1.8432MHz

(%)

Max. Baud rate

with CPR = 1,

TCR = 16

Max. Baud rate

with CPR = 1,

TCR = 4

1.8432

0x08 (1.000)

1.8432

0.00

115,200

460,800

7.3728

0x20(4.000)

1.8432

0.00

460,800

1,843,200

14.7456

0x40 (8.000)

1.8432

0.00

921,600

3,686,400

18.432

0x50 (10.000)

1.8432

0.00

1,152,000

4,608,000

32.000

0x8B(17.375)

1.8417

0.08

2,000,000

8,000,000

33.000

0x8F (17.875)

1.8462

0.16

2,062,500

8,250,000

40.000

0xAE (21.750)

1.8391

0.22

2,500,000

10,000,000

50.000

0xD9 (27.125)

1.8433

0.01

3,125,000

12,500,000

60.000*

0xFF (31.875)

1.8824

2.13

3,750,000

15,000,000

Table 37: Example clock options and their associated maximum baud rates

System Clock (MHz)

Sampling

Clock

TCR

Value

1.8432

7.372

14.7456

18.432

0x00

115,200

460,750

921,600

1.152M

2.00M

2.50M

3.125M

3.75M

0x0F 122,880

491,467

983,040 1,228,800 2,133,333 2,666,667 3,333,333

4.00M

0x0E 131,657

526,571 1,053,257 1,316,571 2,285,714 2,857,143 3,571,429 4,285,714

0x0D 141,785

567,077 1,134,277 1,417,846 2,461,538 3,076,923 3,846,154 4,615,384

0x0C 153,600

614,333 1,228,800 1,536,000 2,666,667 3,333,333 4,166,667

5.00M

0x0B 167,564

670,182 1,340,509 1,675,636 2,909,091 3,636,364 4,545,455 5,454545

0x0A 184,320

737,200 1,474,560 1,843,200

3.20M

4.00M

5.00M

6.00M

0x09

204,800

819,111 1,638,400 2,048,000 3,555,556 4,444,444 5,555,556 6,666,667

0x08

230,400

921,500 1,843,200 2,304,000

4.00M

5.00M

6.25M

7.50M

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

6.40M

8.00M

10.00M

12.00M

0x04

460,800 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.

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