XECOM
(7)
XE24S500
XE24S500 COMMUNICATIONS CONTROLLER
An internal micro-controller serves as the XE24S500
communications controller. This micro-controller
manages the host interface, manages the wireless
link, and formats data for the RF communications.
HOST INTERFACE
The XE24S500 has two primary system interfaces;
the serial interface and the direct sensor interface
supported by SensorOnAir™. The communications
controller manages both interfaces.
Serial Interface
The XE24S500 supports a 4-line serial interface.
Control and configuration of the transceiver takes
place through the serial interface using modem-like
AT commands. The serial data rate is configurable
from 1200 to 115.2K bits per second. The supported
serial interface signals are listed below.
TXD - Transmit Data; input for commands and for
Data to be transmitted on the wireless link.
RXD - Received Data; the output for received RF
data and responses to AT commands.
/RTS - Request to Send, hardware flow control
input. The host raises /RTS to tell the
XE24S500 to stop passing data on RXD.
/CTS - Clear to Send, is the hardware flow control
output. The XE24S500 raises /CTS to stop
data input on the TXD lead.
XE24S500 AT Command Format
Each command follows a standard command
format as described below. Commands are
accepted at data rates from 1200 to 115,200 bps.
The default serial data rate is 9600 bps and is
changed using register S23.
Command Prefix - Each command, except A/,
begins with the AT prefix. The "A" and "T" may be
either both upper case or both lower case but cannot
be of different cases. The prefix identifies parity of
the commands sent to the XE24S500 by comparing
the parity bits of the "A" and the "T" characters.
Command Line - Commands may be strung
together in a single command line of up to 30
characters. Commands in the command string are
executed in the sequence they appear. An
“ERROR” response will be issued if the command
buffer is overfilled and none of the commands will
be executed.
Omitted Parameters - Many commands include a
parameter which determines the function setting.
When the command parameter is omitted from the
command string, it is assumed to be a 0.
Result Codes - Result codes are normally issued
after each action. Result codes may be provided as
full words, numeric codes, or may be disabled.
When numeric result codes are chosen, each result
code ends with a Carriage Return. Full word result
codes are preceded and followed by a Line Feed
and Carriage Return.
Disconnect Sequence - A 3-character sequence
initiates a disconnect of the wireless link.
The
sequence “~~~” is assigned to disconnect the link.
DIRECT CONNECTION OF SENSORS
SensorOnAir™ permits sensors to be connected
directly to the XE24S500 without an application
controller. The XE24S500 communications controller
controls the operation of the sensors.
Sensor I/O Lines™
SensorOnAir™ controls the operation of 6 I/O lines.
This includes 2 analog inputs, ADC0 and ADC1, and
4 digital I/O lines, DIO0, DIO1, DIO2, and DIO3.
ADC0 and ADC1 are connected to a 12-bit analog
to digital converter and use a 2.5 volt reference
derived from VCC as their reference voltage. The
digital I/O lines can be programmed to act as either
inputs or outputs.
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