Quatech QSC(LP)-300 user manual Force High-Speed Uart Clock X8, pins 17

2.1.3 Force High-Speed UART Clock (X8, pins 17 and 18)

This jumper forces an increase of the UART input clock frequency by a factor of 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 this jumper is applied, it overrides any value written to the Options Register to set the clock multiplier by software. The effective baud rate will be eight times the value for which the UART itself is programmed. If selected, the clock multiplier will be applied to all ports on the card, it is not possible to selectively apply the clock multiplier to a specific port.

The factory default is no jumper 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.

Quatech QSC(LP)-200/300 User's Manual 7