Quatech QSC(LP)-100 User Manual

Page 8

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 (see section 4.4).

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

QSC(LP)-100 User's Manual