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2.4.2 Force High-Speed UART Clock (X2, X4, or X8, J10-J12)
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 page 10).
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
J10 | X2 | J10 | X2 |
J11 | X4 | J11 | X4 |
J12 | X8 | J12 | X8 |
J13 | SPAD | J13 | SPAD |
Factory default | Force | ||
software control | Baud rates up to 230.4 kbps | ||
J10 | X2 | J10 | X2 |
J11 | X4 | J11 | X4 |
J12 | X8 | J12 | X8 |
J13 | SPAD | J13 | SPAD |
Force | Force | ||
Baud rates up to 460.8 kbps | Baud rates up to 921.6 kbps |
Figure 5 --- Clock multiplier jumper options
Quatech | 12 |