11
REV. 2.0.1
SP338/SP339/XR34350 EVALUATION BOARD USER’S MANUAL
2.2
Additional Control Signals
2.2.1
SLEW
By default, slew rate limiting is disabled. To enable slew rate limiting, place a jumper between J23 pins 1 & 2.
2.2.2
DIR1
This pin is only applicable in the half-duplex and full-duplex RS-485/RS-422 modes. The DIR1 signal can
manually be controlled at J23 pins 3 & 4. There’s an internal pull-down resistor on this pin. To change the logic
level on this pin, install a jumper at J23 pins 3 & 4.
2.2.2.1
Full-Duplex Mode
In the full-duplex modes, this pin enables/disables the T1 differential driver. A logic low disables the T1
differential driver. A logic high enables the T1 differential driver.
2.2.2.2
Half-Duplex Mode
In the half-duplex modes, this pin controls the direction of the T1 different driver or R1 differential receiver. A
logic low enables the R1 differential receiver and disables the T1 differential driver. A logic high enables the T1
differential driver and disablesthe R1 differential receiver.
2.2.3
DIR2
This pin is only applicable in the half-duplex and full-duplex RS-485/RS-422 modes. The DIR2 signal can
manually be controlled at J23 pins 5 & 6. There is an internal pull-down resistor on this pin. To change the
logic level on this pin, install a jumper at J23 pins 5 & 6.
2.2.3.1
Full-Duplex Mode
In the full-duplex modes, this pin enables/disables the T2 differential driver. A logic low disables the T2
differential driver. A logic high enables the T2 differential driver.
2.2.3.2
Half-Duplex Mode
In the half-duplex modes, this pin controls the direction of the T2 different driver or R1 differential receiver. A
logic low enables the R2 differential receiver and disables the T2 differential driver. A logic high enables the T2
differential driver and disablesthe R2 differential receiver.
2.2.4
TERM
This pin is only applicable in the half-duplex and full-duplex RS-485/RS-422 modes. The TERM pin enables/
disables the internal termination resistor. There is an in internal pull-down resistor on this pin so the internal
termination resistor is disabled when there’s no jumper across J23 pins 13 & 14. Install a jumper across J23
pins 13 & 14 to enable the internal termination resistor.
2.2.5
INVDIR
This pin is only applicable int he half-duplex and full-duplex RS-485/RS-422 modes. The INVDIR inverts the
polarity of the DIR1 and DIR2 pins. This pin has an internal pull-down resistor. The polarity inversion can be
enabled by installing a jumper across J23 pins 15 & 16.
2.2.6
ENABLE
This pin enables/disables the SP338/339/XR34350. This pin has an internal pull-down. When shipped from
the factory, there will be a jumper installed across J23 pins 17 & 18 to enable the SP338/339/XR34350.
