NAL A3LA-R-SMA, User Manual

Page: 18 / 158

A3LA-R User Guide Version A
Document Number: 451-93156-001A 18 of 158
Table 1: Pin Assignments for the Multi-interface Connector
Pin # Signal Description Interface
24 DA_RX PCM digital audio input Digital Audio
25 SIGNAL GND Signal ground, 0 V signal reference and return GND
2.1 RS232 D
ATA
I
NTERFACE
(S
TANDARD
9-W
IRE
C
ONFIGURATION
)
The A3LA-R supports a standard RS232 data interface to a DTE incorporating hardware
handshaking and flow control. The RS232 data interface comprises eight standard RS232 data,
control, and status signals, plus a ground-level signal reference, as shown in Table 1 . This
interface allows a connected DTE to utilize the A3LA-R’s modem functionality through standard
AT and extended sets of AT commands. These commands are defined in Appendix A: AT
Interface . The A3LA-R automatically adjusts to the DTE baud and overrides the +IPR setting
when dissimilar. Autobaud occurs on the following characters: ‘a’, ‘A’, and CR (carriage return).
Autobaud also occurs on the escape sequence character, provided this is an odd number of
characters. Normally this is set to ‘+’ in register S2 (see Appendix A: AT Interface for details).
Note that the Ring Indicator is used by the A3LA-R to indicate that a mobile-terminated SBD
(MT-SBD) message is queued at the gateway. Application developers can monitor this pin and
apply appropriate AT commands to the A3LA-R to retrieve the MT-SBD message.
2.2 RS232 D
ATA
I
NTERFACE
(3-W
IRE
C
ONFIGURATION
)
A 3-wire RS232 data interface may also be implemented. Because of risk of overrun and data
loss, especially at high bauds, the 9-wire interface is the recommended implementation. Take
the steps below to allow 3-wire configuration (i.e., only use S_TX, S_RX, and SIGNAL GND).
These steps ensure the A3LA-R and Data Terminal Equipment (DTE) to work together without
having hardware handshaking.
1. Ensure the modem’s Data Terminal Ready (DTR) line is held high. Using the modem’s
input voltage is fine for this purpose BUT ONLY if the input voltage is less than 5 VDC
(see important note below). Looping back the modem’s DSR line to DTR line will NOT
work. Leave the Data Set Ready (DSR) line on the modem unconnected.