Campbell Scientific RF310, RF312, RF313 Narrowband Radios - Manual (Page 64)

Appendix E. RF310M States
E-2
is transmitted on the rising edge of CLK/HS. The RF310M completes
addressing when the eighth bit is received.
The synchronous device capability enables the Datalogger to have measurement
capability at a phone-to-RF base station. A command within the address sent to
the RF310M can tell the RF310M to connect to the phone modem which
requires the RF310M to switch its TXD and RXD lines. Therefore all
characters are routed through the phone modem to the RF310M which controls
the radio accordingly.
The RF310M then enters the Active State. The receiver is enabled when SDE
and CLK/HS are high. The transmitter is enabled when SDE is high and
CLK/HS is low.
In the Active State, the RF310M responds to the commands S, R, T, F, and U.