Omega Engineering OMG-COMM8-A appendix Appendix E 3421 Addendum

Appendix E – 3421 Addendum

Appendix E - 3421 Addendum

The OMG-COMM8-Acan be equipped with a higher speed oscillator and the Startech 16C654 UART. This UART has a significantly larger FIFO (64 bytes as opposed to the 16 of the 16C554). The OMG-COMM8-Aequipped in this manner can be ordered as the part number 3421.

The 3421 has a 7.3728 MHz oscillator, as opposed to the standard 1.8432 MHz oscillator, that allows data rates up to 460.8 K bps. To use the 3421 with a standard communications package, or to achieve standard data rates (i.e. 1200, 2400, 9600…115.2K) simply select a data rate that is your target data rate divided by 4. For example, if you need a data rate of 9600, you would choose 2400, 9600 ÷ 4 = 2400.

The following table shows some common data rates and the rates you should choose to match them.

For this Data Rate	Choose this Data Rate
1200 bps	300 bps
2400 bps	600 bps
4800 bps	1200 bps
9600 bps	2400 bps
19.2K bps	4800 bps
38.4K bps	9600 bps

If your communications package allows the use of Baud rate divisors, choose the appropriate divisor from the following table:

For this Data Rate	Choose this Divisor
1200 bps	384
2400 bps	192
4800 bps	96
9600 bps	48
19.2K bps	24
38.4K bps	12
57.6K bps	8
115.2K bps	4
230.4K bps	2
460.8K bps	1

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