Rabbit 2000™ Microprocessor Designer's Handbook

> ## Appendix A. Supported Rabbit 2000 Baud Rates

> This table contains divisors to put into TATxR registers. All frequencies that allow 57600 baud up to 30MHz are shown (as well as a few higher frequencies):

> Crystal Freq. (MHz) | Example Boards | 2400 baud | 9600 baud | 19200 baud | 57600 baud | 115200 baud
> 1.8432 |  | 23 | 5 | 2 | 0 | -
> 3.6864 | BL1800 divided by 8 | 47 | 11 | 5 | 1 | 0
> 5.5296 |  | 71 | 17 | 8 | 2 | -
> 7.3728 | BL1810, not doubled | 95 | 23 | 11 | 3 | 1
> 9.2160 | RCM2020, not doubled | 119 | 29 | 14 | 4 | -
> 11.0592 | RCM2100, not doubled | 143 | 35 | 17 | 5 | 2
> 12.9024 | RCM2000. not doubled | 167 | 41 | 20 | 6 | -
> 14.7456 | BL1820, doubled | 191 | 47 | 23 | 7 | 3
> 16.5888 |  | 215 | 53 | 26 | 8 | -
> 18.4320 | TCP/IP Dev. Kit | 239 | 59 | 29 | 9 | 4
> 20.2752 |  | * | 65 | 32 | 10 | -
> 22.1184 | RCM2100, doubled | * | 71 | 35 | 11 | 5
> 23.9616 |  | * | 77 | 38 | 12 | -
> 25.8048 | RCM2010, doubled | * | 83 | 41 | 13 | 6
> 27.6480 |  | * | 89 | 44 | 14 | -
> 29.4912 | BL1800 (can't double) | * | 95 | 47 | 15 | 7
> 36.8640 |  | * | 119 | 59 | 19 | 9
> 44.2368 |  | * | 143 | 71 | 23 | 11

> This information is calculated with the following equation:

>     divisor = (crystal frequency in Hz) / (32 * baud rate) - 1

> If the divisor is not an integer value, that baud rate is not available for that frequency (identified by a "-" in the table).

> If the divisor is above 255, that baud rate is not available without further BIOS modification (identified by a "*" in the table). To allow that baud rate, you need to clock the serial port desired via timer A (by default they run off the CPU clock / 2), then scale down timer A to make the serial port divisor fall below 256.

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