User`s manual

COMHP 7404/-D25 CyberResearch

Serial Communications

Clock Modes

The COMHP 7404 employs a unique clocking option that allows the end user to select from divide by 4, and divide by 1

clocking modes. These modes are selected at Header J1.

To select the Baud rates commonly associated with COM: ports (i.e. 2400, 4800, 9600, 19.2, … 115.2K bps) place the

jumper in the divide by 4 mode (silk-screen D4).

To select the Baud rates above 115.2K select the divide by 1 mode (silk-screen D1).

Baud Rates and Divisors for the ‘DIV1’ mode

The following table shows some common data rates and the rates you should choose to match them if using the adapter in the

‘DIV1’ mode.

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

57.6 K bps 14.4K bps

115.2 K bps 28.8K bps

230.4K bps 57.6 K bps

460.8K bps 115.2 K 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