Quatech QSC-100 User Manual

Page 9

2.3 Force High-Speed UART Clock (X2, X4, or X8, J3-J5)

These jumpers force an increase of the UART input clock frequency by a factor of

two, four, or eight. This feature can allow legacy software to use baud rates above
115,200 bits per second. It is also useful if the serial port device driver does not directly
support setting the higher baud rates through the Options Register.

If one of these jumpers is applied, it overrides any value written to the Options

Register to set the clock multiplier by software. The effective baud rate will be either
two, four, or eight times the value for which the UART itself is programmed.

The factory default is none of these jumpers applied, which allows for software

control of the clock multiplier via the Options Register. The Options Register powerup
default is for a standard times-1 clock of 1.8432 MHz for compatibility with standard
serial ports.

SPAD

Force times-eight clock

Baud rates up to 921.6 kbps

SPAD

Force times-two clock

Baud rates up to 230.4 kbps

SPAD

Factory default

software control

SPAD

Force times-four clock

Baud rates up to 460.8 kbps

Figure 4 --- Clock multiplier jumper options

Quatech QSC-100 User's Manual