B&B Electronics 232MSS2 - Manual (Page 12)

Documentation Number 232MSS2-0108 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445
8
Smart Switch/Port Combiner Mode
This mode allow Ports A-D to select the master port using a
handshake line. It also allows selection from the master port via the
preamble code described in the Smart Switch Only Mode section.
Position 7 of “SW1” must be ON to be in port combiner mode. When
a handshake line goes high on any of the four ports, it will establish
a connection from that port to the master port. This works on first-
come-first-serve basis. If multiple ports have their handshake lines
high, the port that has been waiting the longest will be next to be
connected to the master port. For example: (Initial conditions -- no
slave ports with handshake lines asserted.) In chronological order,
Port C asserts its handshake line, Port A asserts its handshake line,
Port D asserts its handshake line and then Port C disasserts its
handshake line. When Port C asserts its handshake line, a
connection will be made between the master port and Port C. When
Port C disasserts its handshake line, Port C will disconnected and
Port A will be connected to the master port. When Port A disasserts
its handshake, Port A will be disconnected and Port D will be
connected to the master port.
The handshake line that is used to connect to the master port
depends on the configuration of the master port (which in turn
determines the configuration of the slave ports). If the master port is
configured as a DTE port, then the slave ports are configured as
DCE and RTS must be raised to connect to the master port. If the
master port is configured as a DCE port, then the slave ports are
configured as DTE and CTS must be raised to connect to the master
port.
For example, port A is configured as a DTE port. In order to
establish a connection to the master port, port A must set CTS high
(assert). The 232MSS2 would recognize this as a prompt for
connection to the master port. The connection would be dropped as
soon as CTS on port A is brought low. Ports B-D may raise CTS at
any time to request a connection. However, if port A is connected to
the master port, any data sent from the devices on ports B-D to the
232MSS2 will be lost. The 232MSS2 does not have any buffering.
NOTE: When a port is selected via the Master Port, the
handshake lines will be ignored until the Master Port sends
the turn off code. When the Master Port is selected by a
handshake line, all preamble codes will be ignored.