WI-MOD-9-D
Radio Modem
User Manual v1.9
WI-MOD-9-D
Manual
v 1.9
Page
26
approx 2msec after the end of the message. For example, a message with 20 bytes of data
transmitted at 19200 bits/sec with no repeaters, will be output approx 44msec after the data is
input, assuming that error checking is configured.
There is a special configuration of controlled mode which provides a 5msec lead-in time for fast
operation (see below). With the fast operation, the time to transmit 20 bytes at 19200 baud is
less than 20 msec.
There are several configurations for controlled mode:
3.6.1 Auto-Connect Controlled Mode
Auto-connect mode is similar to “fixed line” modem operation. The master unit wants to
connect to only one slave address. Normally the slave address is preconfigured. On power up,
the master unit continuously tries to connect to the slave address. The slave unit, on power up,
does not try to connect but waits for a connect message. Once a connection is made, the DCD
status at both ends is set and data can be transferred in either direction. If there is no data transfer
within the preconfigured “link check” time, the master will send a connect message to check the
communications link.
The connection will be broken if a communication failure occurs, or if one of the hosts issues a
“disconnect” AT command (although this would be unusual for this mode). When the master is
disconnected, it will continuously try to connect to its auto-connect address.
Up to five repeater addresses may be configured as part of the auto-connect address. That is, up
to 5 intermediate modules can act as repeaters between the master and slave modules.
3.6.2 Low Power Auto-Connect Mode
For special installations, the WI-MOD-9-D may be operated in a low power condition where it
switches off its receiver - power consumption is reduced to approx 30% of normal. The low
power condition will occur if the WI-MOD-9-D is configured for auto-connect mode AND if the
low power mode feature is configured. The DTR signal on the RS232 port will control switching
between low power and normal operation. When DTR is “low”, the module will change to low
power operation, reset any connected link and switch off its receiver. When DTR goes “high”,
the module will revert to normal operation and will auto-connect to its slave address.
The use of this low power operation may be applicable in remote locations where there is a
limited power supply such as solar panels. In this situation, the DTR signal from the host device
is used to “wake-up” the WI-MOD-9-D unit. The WI-MOD-9-D unit will then operate normally
until the DTR signal is reset by the host device.
3.6.3 Single-Connect Controlled Mode
Single-connect is similar to a dial-up modem. In this mode, the module will only make one
attempt to connect to a destination address. A host device will issue a connect AT command,
and the module will send a connect message to the destination address. If the destination module
responds, then the link is connected and the DCD status is set. If the destination module does
not respond, then the link is not established and no data can be transferred. The module will not
attempt to reconnect again until it receives another connect command from its host.