Rose Electronics Porter - Manual (Page 20)

Operation
16 PORTER INSTALLATION AND OPERATIONS MANUAL
Initial state
Following the successful completion of its power up test, the Porter turns all its LEDs off.
The port LEDs will display the initial connect state (all dark for null destination, several lit
for broadcast mode, or one lit for single port connect). The status LEDs will display the
current port activity.
Operating Modes
The Porter has several operating modes. Normal, null destination, and broadcast modes
are used for data transfer. Configuration (menu) mode is used to set up the unit.
Diagnostic mode is used to check the unit for faults. Manual mode allows front panel
switches to change the currently connected port.
Normal mode
Data flow is controlled by sending commands which may be intermixed with data. The
port selected may be changed by sending the proper command. When a port is selected,
normal communication occurs between the master port and the selected port. For serial
models full duplex communication is in effect; data may flow in either direction between
the master port and the selected port. For parallel models data is strobed into the master
port and out of the selected port. Also the status signals such as “PAPER END” are
passed through. Different protocols may be I effect on each port with the Porter making
the conversions automatically.
Sending data from the master to the selected port
When transmitting data from the master port to the selected port the data will
immediately be sent unless the selected port is busy, in which case the data will go into
the selected port’s transmit buffer memory. If the buffer becomes full, the master port
will be signaled to stop sending data according to the flow control protocol set for it.
When a new port is selected and data remains in the previously selected port’s buffer,
data will continue to be sent from the previous port’s buffer to the device it is connected
to according to the flow control protocol currently in operation. Further data sent from
the master will go to the newly selected port or its buffer. Thus each port has its own
transmit buffer memory and data may be transmitted from each port’s buffer memory
simultaneously.
Receiving data from a selected port
Data may be received from a selected port only on the serial models. Parallel units do not
allow incoming data on ports 1-8. Data received from a selected port will be immediately
sent out on the master port unless the master port is bus, in which case the data will go
into the selected port’s receive buffer. If the buffer becomes full the selected port will be
signaled to stop sending data according to the flow control protocol in operation.
Data received on a port which is not selected will be put in to that port’s receive buffer. If
a new port is selected which has data in it’s receive buffer, that data will immediately be
sent to the master port according to the flow control protocol in operation. Further data
received on the newly selected port will be sent to the master port immediately or placed
at the end of data currently in the buffer.
Null destination
When the null destination (prefix + 9) command is in effect, no ports are considered
connected. Any data received on ports 1-8 will go into the respective receive buffer. All
the port LEDs remain off. Commands received via port 0 will continue to be recognized,
all other data received on port 0 is discarded. Null destination is terminated by sending
another connect command or the broadcast mode command.