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2.3 Force High-Speed UART Clock (X2, X4, or X8, J5-J7)
These jumpers force an increase of the UART input clock frequency by a factor of
two, four, or eight. This 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 page 12).
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
X2
X4
X8
J5
J6
J7
J8
Force times-eight clock
Baud rates up to 921.6 kbps
SPAD
X2
X4
X8
J5
J6
J7
J8
Force times-two clock
Baud rates up to 230.4 kbps
SPAD
X2
X4
X8
J5
J6
J7
J8
Factory default
software control
SPAD
X2
X4
X8
J5
J6
J7
J8
Force times-four clock
Baud rates up to 460.8 kbps
Figure 4 --- Clock multiplier jumper options
Quatech DSC-100 User's Manual
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