BusWorks
Model 903MB/902MB/901MB Network I/O Module User’s Manual Digital I/O
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Host Communication
Set via the Settings pull-down menu
Host – Communications Port:
COM1-COM4 can be selected
via the scroll window, or you can type in any COM port from
COM1 to COM99.
Host – Baud Rate:
Select 2400, 4800, 9600 (default), 14400,
19200, 28800, 38400, 57600, 76800, or 115200 bits per
second.
Host – Parity:
Select Even, Odd, or None (See Parity Checking)
for error checking. The odd or even parity bit is followed by 1
stop bit. If None is selected, 1 or 2 stop bits are used.
Host – Slave Address:
Select a valid slave address in the range
of 1-247 (01H-F7H). Address 247 is used to address a slave
in the default mode.
Host – Update Communication Settings at Download:
Used
to cause the host software to automatically change its
communication parameters to match those set at the
connected module following a download to it.
Slave Communication
Slave – ID:
The Report Slave ID command will return the model
number, run on/off status, firmware/model string, and module
serial number.
Slave – Reset:
This command is used to trigger a reset of the
module and its effect is equivalent to a power-on reset. An
alternate method of resetting a module can be accomplished
via a write to the Calibration Access & Reset Register (see
Reset Register 40011). This is provided to accomplish reset
with software that does not support the Reset Slave
command.
Slave – Address:
Select valid slave addresses in the range of 1-
247 (01H-F7H). Address 247 is the default mode slave
address.
Slave – Baud Rate:
Select 2400, 4800, 9600 (default), 14400,
19200, 28800, 38400, 57600, 76800, or 115200 bits per
second.
Slave – Parity:
Select Even, Odd, or No Parity (See Parity
Checking) error checking. Odd or even parity bit is followed
by 1 stop bit. If no parity is selected, 1 or 2 stop bits are
used.
Slave - Response Delay:
Can be set from 0-65500 ticks (1 tick
= 1.085us) and refers to the additional delay a module will
wait before it sends its response to a message from the host.
Some signal converters or host/software systems cannot
accept a response to a message immediately after sending
the message without additional delay.
Slave – Status:
The Module Status Register can be used to
determine the internal flash or EEPROM checksum error
status. It also includes port watchdog timeout flags.
Slave – Watchdog:
A watchdog timer may be applied to each
I/O port of this module (port 0 = I/O channels 0-3, port 1 = I/O
channels 4-7, port 2 = I/O channels 8-11). Use the Port
Watchdog Time Register to select a timeout period from 1 to
65534 seconds (18.2 hours). A time of 65535 (FFFFH) will
disable the watchdog timer for the port. Use the Port
Timeout State Register to define the states that the outputs
of the port are to be programmed to upon timeout. The four
lower order bits of this register value define the timeout states
of each of the port output channels. Writing 65535 (FFFFH)
to this register will leave the port outputs unchanged upon
timeout. A port watchdog fault indication flag (bits 2-0 of the
Module Status register) will be set if any of the port output
channels have not been written to over the specified time
period, or if any of the port input channels have not been read
over the specified time period.
In addition, the module status LED will blink rapidly if a
watchdog timeout occurs (Note: A slow blink rate indicates
the module is in the default communication mode and a
timeout may temporarily mask default mode indication). The
port watchdog timer is reinitiated via a read or write to any
input/output channel of the same port.
Digital Input
No Channel Configuration Required.
Input – Read State:
Use the Read Input Status Command to
read the status of the input/output channels. Note that the
Read Input Status command will also reinitiate the port
watchdog timer if enabled.
Input – Indication:
The current input state is indicated by a
yellow status LED at the front of the module—LED is ON
when input is low (or tandem output is sinking current), and
OFF when input is high (or tandem output not conducting).
Digital Outputs
No Channel Configuration Required.
Output – Read State:
Use the Read Coil Status Command to
read the status of the output channels. This is equivalent to a
read of the gate signal of the n-channel mosfet driving the
output. As such, it may not reflect the actual output state if
the output is not pulled-up or has no excitation.
Output – Write State:
Use the Force Single Coil command or
Force Multiple Coils command to turn the outputs ON or
OFF. Note that the Force Coil commands will also reinitiate
the port watchdog timer if enabled.
Output – Indication:
The current output state is indicated by a
yellow status LED at the front of the module—LED is ON
when output is ON or sinking current.
Output – Timeout State:
Use the Port Timeout State Register
to define the states the outputs of the port are to be
programmed to upon watchdog timeout. The four lower order
bits of this 16-bit value define the timeout states of each of
the port output channels. Writing 65535 (FFFFH) to this
register will leave the port outputs unchanged upon timeout.
Note that clearing a timeout via a read or write to any port I/O
channel does not return the output to its pre-timeout state.
The output remains in its timeout state until otherwise written.
Other Modbus Configuration Software Capabilities
In addition to configuring all features of the module described
above, the Modbus Configuration Software includes additional
capabilities for testing and control of this module as follows:
1.
Monitors the discrete I/O signal states and watchdog status.
Allows discrete outputs to be turned on or off. It also allows
polling to be turned on or off.
2.
Allows a configuration to be uploaded or downloaded to/from
the module via the RS485 interface.
3.
Provides controls to reset a module.
4.
Reads the contents of the Module Status Register.
5.
Allows optional user documentation to be saved with a
module file. Documentation fields are provided for tag
number, comment, configured by, location, and identification
information. This information can also be uploaded from the
module and printed via this software.
6.
Allows a module’s complete configuration to be printed in an
easy to read, single-page format, including user
documentation.
