/* Imported from Wayback Machine

 Original URL : https://retrobrewcomputers.org/doku.php?id=boards:ecb:zilog-peripherals:clock-divider
 Snapshot date: 2025-02-14
 Generator    : wayback-archiver

*/

Z80 SIO divider & jumper table for standard crystals:

The available board rates that can be provided by the SIO/DART are determined by the selection of:

Crystal clock selection

Clock divider selector X5

SIO/DART internal clock divider.

A wide range of board rates can be selected through this combination but for any Crystal:Divider selection, only four board rates are available to be selected by software control.

For example, with a 4.9152Mhz crystal and X5 set for a /8 divider by link pins 9-11 the available baud rates that can be selected through software are 614400, 38400, 19200 and 9600 baud.

Note /1 divider is not available for selection on X5 but is shown for completeness.

X5 JUMPER	1.8432	Mhz		2.4576	Mhz		4.9152	Mhz		7.3728	Mhz
	1843200	Div	Baud	2457600	Div	Baud	4915200	Div	Baud	7372800	Div	Baud
NO DIV	1843200	1	1843200	2457600	1	2457600	4915200	1	4915200	7372800	1	7372800
/1		16	115200		16	153600		16	307200		16	460800
		32	57600		32	76800		32	153600		32	230400
		64	28800		64	38400		64	76800		64	115200
Q0A 13-14	921600	1	921600	1228800	1	1228800	2457600	1	2457600	3686400	1	3686400
/2		16	57600		16	76800		16	153600		16	230400
		32	28800		32	38400		32	76800		32	115200
		64	14400		64	19200		64	38400		64	57600
Q1A 11-12	460800	1	460800	614400	1	614400	1228800	1	1228800	1843200	1	1843200
/4		16	28800		16	38400		16	76800		16	115200
		32	14400		32	19200		32	38400		32	57600
		64	7200		64	9600		64	19200		64	28800
Q2A 9-11	230400	1	230400	307200	1	307200	614400	1	614400	921600	1	921600
/8		16	14400		16	19200		16	38400		16	57600
		32	7200		32	9600		32	19200		32	28800
		64	3600		64	4800		64	9600		64	14400
Q3A 8-10	115200	1	115200	153600	1	153600	307200	1	307200	460800	1	460800
/16		16	7200		16	9600		16	19200		16	28800
		32	3600		32	4800		32	9600		32	14400
		64	1800		64	2400		64	4800		64	7200
Q0B 7-8	57600	1	57600	76800	1	76800	153600	1	153600	230400	1	230400
/32		16	3600		16	4800		16	9600		16	14400
		32	1800		32	2400		32	4800		32	7200
		64	900		64	1200		64	2400		64	3600
Q1B 6-8	28800	1	28800	38400	1	38400	76800	1	76800	115200	1	115200
/64		16	1800		16	2400		16	4800		16	7200
		32	900		32	1200		32	2400		32	3600
		64	450		64	600		64	1200		64	1800
Q2B 3-5	14400	1	14400	19200	1	19200	38400	1	38400	57600	1	57600
/128		16	900		16	1200		16	2400		16	3600
		32	450		32	600		32	1200		32	1800
		64	225		64	300		64	600		64	900
Q3B 3-4	7200	1	7200	9600	1	9600	19200	1	19200	28800	1	28800
/256		16	450		16	600		16	1200		16	1800
		32	225		32	300		32	600		32	900
		64	112.5		64	150		64	300		64	450

Spreadsheet