XStream
‐
PKG
‐
T™
Telephone
RF
Modem
–
Product
Manual
v5.x00
[2006.02.24]
2.2.3.
Binary Command Mode
Sending and receiving parameter values using binary commands is the fastest way to change
operating parameters of the XStream RF Modem. Binary commands are used most often to
sample signal strength (RS parameter) and/or error counts; or change modem addresses and
channels for polling data systems. Since the sending and receiving of register values takes place
through the same serial data path as 'live' data (received RF payload), interference between the
two types of data can be a concern.
Common questions about using binary commands:
•
What are the implications of asserting CMD while live data is being sent or received?
•
After sending serial data, is there a minimum time delay before CMD can be asserted?
•
Is a delay required after CMD is de-asserted before payload data can be sent?
•
How does one discern between live data and data received in response to a command?
The CMD pin must be asserted in order to send binary commands to the RF modem. The CMD pin
can be asserted to recognize binary commands anytime during the transmission or reception of
data. The status of the CMD signal is only checked at the end of the stop bit as the byte is shifted
into the serial port. The application does not allow control over when data is received, except by
waiting for dead time between bursts of communication.
If the command is sent in the middle of a stream of payload data to be transmitted, the
command will essentially be executed in the order it is received. If the radio is continuously
receiving data, the radio will wait for a break in the received data before executing the command.
The
signal will frame the response coming from the binary command request [refer to Figure
below].
A minimum time delay of 100 µs (after the stop bit of the command byte has been sent) must be
observed before the CMD pin can be de-asserted. The command executes after all parameters
associated with the command have been sent. If all parameters are not received within 0.5
seconds, the modem returns to Idle Mode.
Note: When parameters are sent, they are two bytes long with the least significant byte sent first.
Binary commands that return one parameter byte must be written with two parameter bytes.
Commands can be queried for their current value by sending the command logically ORed (bit-
wise) with the value 0x80 (hexadecimal) with CMD asserted. When the binary value is sent (with
no parameters), the current value of the command parameter is sent back through the DO pin.
Figure
2
‐
09.
Binary
Command
Write
then
Read
Signal
#4
is
CMD
Signal
#1
is
the
DIN
signal
to
the
radio
Signal
#2
is
the
DOUT
signal
from
the
radio
Signal
#3
is
In
this
graph,
a
value
was
written
to
a
register
and
then
read
out
to
verify
it.
While
not
in
the
middle
of
other
received
data,
note
that
the
signal
outlines
the
data
response
out
of
the
modem
IMPORTANT:
For the RF Module to recognize a binary command, the RT (DI2 Configuration)
parameter must be set to one. If binary programming is not enabled (RT
≠
1), the
RF module will not recognize that the CMD pin is asserted and therefore will not
recognize the data as binary commands.
©
2006
MaxStream,
Inc.,
Confidential
and
Proprietary
18
