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Appendix E – 3421 Addendum
Omega Engineering OMG-COMM8-A Page 17
Appendix E - 3421 Addendum
The OMG-COMM8-A can 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-A
equipped 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