Commercial In Confidence
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Note that if RTS is dropped before a dial up command has been completed the link members
will be left in an undefined state waiting to time out. Also if the dialling radio is power saved
it will return to sleep before completing transmission of the AT error code to the host
resulting in corrupt serial data. It is therefore recommended that RTS should not be dropped
until commands have been completed and the appropriate error codes returned.
The operation of the hardware handshakes lines can be summarised as follows:
RTS when raised is a signal to the radio to wake up and enter command mode. Dropping
RTS cancels all operations and returns the radio to sleep.
CTS when raised provides acknowledgement that the radio is awake, or when dropped that
the radio is entering sleep.
DCD when raised is an indication that a link has been established and that transparent mode
is active, it is dropped when the link fails or is terminated.
RI when raised is an indication that an incoming call is being received.
5.2.4
RADIO
ROUTING
Routing is determined by the dial up command used by the calling host. Radios will pass on
route information to all members of a link at the point of call set up. When a radio calls
another radio either because its host has requested a dial up or because it has been told by
another radio that it is to be part of a link, it first sends a wake up request to the next radio in
the route and waits for a reply, when this is received the route information is sent, no reply is
required to this message, the next message expected is a link fail or link established message
originating from the final destination radio. When received the link established message is
forwarded on to the original calling radio. If a radio fails to respond to the wake up signal the
radio calling it will return the address of the failed radio in the link fail message, a final
destination radio may also reply with a message indicating that the destination host did not
respond to the wake up procedure. This data is returned to the host by appending the "NO
ANSWER" error message with the failed address in ASCII numerals or the message "NO
PICK UP". If no link failed/established is received "NO ANSWER" is returned on its own.
5.2.5
WAKE
UP
PROCEDURE
Some radios in a network may have mains power supplies available and so do not need to
conserve power by sleeping, to accommodate such radios a single wake up message is sent
and a 1 second wait (programmable via the AT S registers) is imposed to allow a reply, a
radio knows whether the radio it is calling should be sleeping or not from its address value.
If the destination is a sleeping radio the wake up message is sent cyclically for 6 seconds
(programmable via the AT S registers) to allow a sleeping radio to hear it, when this is
completed a reply is waited on again for 1 second.
5.2.6 IMPLEMENTED
S
REGISTERS
S0 AUTO
ANSWER
Sets the number of seconds to wait after raising RI before entering transparent mode or if
zero waits for the host to respond with an ATO command (up to the time set by S21).
S1 not
implemented
S2 ESCAPE
CHARACTER
Sets the value used for the 3 character escape code.
S3 to S11
not implemented
