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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
X2
X4
X8
J3
J4
J5
J6
Force times-eight clock
Baud rates up to 921.6 kbps
SPAD
X2
X4
X8
J3
J4
J5
J6
Force times-two clock
Baud rates u
p
to 230.4 kb
p
s
SPAD
X2
X4
X8
J3
J4
J5
J6
Factory default
software control
SPAD
X2
X4
X8
J3
J4
J5
J6
Force times-four clock
Baud rates up to 460.8 kbps
Figure 4 --- Clock multiplier jumper options
Quatech QSC-100 User's Manual 7