© 2014 Exar Corporation
XR21B1424IV64-0A-EVB
4 / 6
exar.com/XR21B1424
Rev 1A
GPIO6/CLK
When shipped from the factory, the GPIO6/CLK pin is floating. If using this pin as a CLK function, the signal can be cap-
tured via the J31 header. If using this pin to control the MODE0 pin of the SP339, install jumpers for the appropriate chan-
nels listed in Table 5. The software driver/application will need to control the state of this pin.
GPIO7/RS485
When shipped from the factory, the GPIO7/RS485 pin is floating. This pin can be used to control the DIR1 pin of the SP339
when the SP339 is configured for half-duplex RS-485 mode. If using this pin to control the DIR1 pin of the SP339, install
jumpers for the appropriate channels listed in Table 6. The software driver/application will need to enable the half-duplex
direction control feature for this pin.
GPIO8/TXT
When shipped from the factory, the GPIO8/TXT pin is floating. This pin can be used to control the MODE1 pin of the SP339.
If using this pin to control the MODE1 pin of the SP339, install jumpers for the appropriate channels listed in Table 7. The
software driver/application will need to control the state of this pin.
Table 5: Default Jumper Setting for GPIO6/CLK
Jumper Setting
Description
J5 - 1& 2
Not installed. GPIOA6/CLKA is not connected to the MODE0 pin of the SP339.
J10 - 1& 2
Not installed. GPIOB6/CLKB is not connected to the MODE0 pin of the SP339.
J11 - 1& 2
Not installed. GPIOC6/CLKC is not connected to the MODE0 pin of the SP339.
J20 - 1& 2
Not installed. GPIOD6/CLKD is not connected to the MODE0 pin of the SP339.
Table 6: Default Jumper Setting for GPIO7/RS485
Jumper Setting
Description
J3 - 1& 2
Not installed. GPIOA7/RS485A is not connected to the DIR1 pin of the SP339.
J10 - 1& 2
Not installed. GPIOB7/RS485B is not connected to the DIR1 pin of the SP339.
J11 - 1& 2
Not installed. GPIOC7/RS485C is not connected to the DIR1 pin of the SP339.
J20 - 1& 2
Not installed. GPIOD7/RS485D is not connected to the DIR1 pin of the SP339.
Table 7: Default Jumper Setting for GPIO8/TXT
Jumper Setting
Description
J5 - 3 & 4
Not installed. GPIOA8/TXTA is not connected to the MODE1 pin of the SP339.
J10 - 3 & 4
Not installed. GPIOB8/TXTB is not connected to the MODE1 pin of the SP339.
J11 - 3 & 4
Not installed. GPIOC8/TXTC is not connected to the MODE1 pin of the SP339.
J20 - 3 & 4
Not installed. GPIOD8/TXTD is not connected to the MODE1 pin of the SP339.
