Chapter Two
Operation
MAN_905G_1.16
Page 20
binary/digital read command, the 905G will convert the 16 bit value into a binary (1 bit)
value before it responds.
An example of normal operation - assume that a remote module has address 14 and the
905G is address 1. Module #14 is configured with a mapping DI1
→
I/O Reg 76 at #1.
When DI1 turns "on", module #14 transmits a message. If the 905G can hear this message, it
will transmit an acknowledgment back to module #14, and updates the value of I/O register
76 in the 905G database. The host device can read I/O register 76 via the data-bus, or the
905G may write the value of I/O register 76 to the host device.
I/O registers that receive values from other 905U or G modules via radio are configured with
a “Communications fail time”. If the 905G does not receive a message for this I/O register
within the comms-fail time, then the I/O register is given a “comms fail” status which the
host device can read.
I/O registers that transmit out to other 905U or G modules are configured with an “update
time” and a “sensitivity”. The 905G will transmit a message to the configured remote output
whenever the I/O register value changes by the sensitivity amount – if it has not changed
within the update time, the 905G will send a message anyway. The 905G will make five
attempts to send a message - if it does not receive an acknowledgment from the remote
module, then the I/O register is given a “comms fail” status which the host device can read.
Each I/O register has an associated “status” register, which includes information such as
comms-fail status. As well as each I/O register having an individual comms-fail status, each
remote module has an overall comms fail status. This status is “set” (on) whenever a comms-
fail occurs for an individual I/O register, and is “reset” (off) whenever a message is received
from the remote module. The 905G can be configured to not send any update messages to a
remote module if it senses that the remote module is in “comms fail” - that is, if any I/O
register associated with the remote module is in “comms fail”. It will start sending update
messages again when the 905G receives a message from the remote module. The default
configuration is that output updates ARE sent during comms fail conditions.
905U-G
905U-1
DIN1
#14
#1