Campbell Scientific RF310, RF312, RF313 Narrowband Radios - Manual (Page 63)

E-1
Appendix E. RF310M States
The RF310M Modem operates in one of two separate states. The RF310M can be utilized
in either the RF310M-ME (Modem Enable) State or the RF310M-SDC (Synchronous
Device Communication) State. The RF310M-ME State is normally used for all RF
networks. The RF310M-SDC State must be used when there is a phone-to-RF base station
with a datalogger. Note: the 21X and CR7 dataloggers don’t support the SDC state. A
switch inside the RF310M needs to be set according to the chosen state.
E.1 RF310M-ME State
The RF310M-ME State is always used with 21X and CR7 dataloggers, and
normally with all other dataloggers.
RF310M-ME State Description
The RF310M rings the datalogger until the datalogger raises the ME line. The
Datalogger waits approximately 40 seconds to receive carriage returns to
establish the baud rate. After the baud rate is set the Datalogger transmits a
carriage return, line feed, "*", and enters the Telecommunications Mode. If the
carriage returns are not received within the 40 seconds, the Datalogger hangs
up.
When the datalogger is in the Telecommunications Mode, the ME line is high,
and the RF310M is subsequently in the Transparent Mode or EOL Mode
depending on the relative location of the RF310M.
E.2 RF310M-SDC State
The RF310M-SDC State can be used to enable a Datalogger to be recording
measurements at a phone-to-RF base station. The SDC State is never used with
21X or CR7 dataloggers.
RF310M-SDC State Description
The RF310M obeys all Synchronous Device Communication (SDC) protocol
when set in the RF310M-SDC State. Most dataloggers have the ability to
address synchronous devices. The 21X and CR7 do not support the SDC state.
The Datalogger and the RF310M use a combination of the Ring (pin 3),
Clock/Handshake (pin 7), and Synchronous Device Enable (SDE, pin 6) lines
to establish communication rather than just the Modem Enable line.
When the Datalogger is connected to the RF310M, a 1N command is sent to
the datalogger at setup. The baud rate is set and the Datalogger completes
connections with the RF310M. The Datalogger sets the RF310M in an
addressing state by raising the CLK/HS followed by or simultaneously raising
the SDE line. The RF310M drops the ring line and prepares for addressing.
The Dataloggger then synchronously clocks 8 bits (the address) onto TXD
using CLK/HS as a clock. The least significant bit is transmitted first, each bit