Documentation Number 232PTC3401 - pg. 1/2
1996 B&B Electronics -- Revised September 2001
This product designed and manufactured in USA of domestic and imported parts by
RS-232 Port Combiner
CE
Model 232PTC
Introduction
B&B Electronics' Model 232PTC permits two or more serial devices to share
a serial port on a host computer. When one of the devices on either of the slave
ports transmits data, it captures the data path to the master port and locks out the
other slave port. When data transmission is finished, either slave port gets access
to the master port by being the first to start sending data. The RTS line can also be
used to control data flow to the master port. The 232PTC can be cascaded to
combine as many devices as needed into one host port. A typical application would
be to share one host port with several terminals, scanners, scales, or other devices
that only need access to the host port occasionally as shown in Figure 1.
Operation
Data flow from master port to slave ports
All data that is sent to the TX line, pin 2 on the master port, is broadcast to
both slave ports under all conditions. This data appears on pin 3 of each slave
port.
Data flow from slave ports to master port
Data that is sent to the TX line (pin 2) on the slave ports must compete for the
path to the master port. There are two methods of capturing the path to the
master port, RTS and automatic data sensing. The first slave port to either raise
its RTS line or transmit data captures the path to the master port. The path will be
locked on that slave port until it either lowers its RTS line, or 50 milliseconds after
the end of its transmission. Note that the 232PTC does not buffer any data, any
data sent to the opposite slave port during this period will be lost. The 50ms
timeout period can be modified, contact B&B's technical support for further
information.
Handshake Signals
The CTS signal on each slave port indicates to the slave devices if the path to the master port is available. If the slave
port's CTS line is high, data received by that port will be transmitted out the master port. If CTS is low, the opposite slave
port has captured the path to the master and any data at the inactive slave port will be lost. For example, if both slave ports
are inactive and have RTS low, CTS will be high at both slave ports, indicating that the path is available. As soon as one
slave port captures the path by either beginning its transmission or raising its RTS line, the CTS signal at the opposite
slave port will drop to the low state.
The RTS output on the pin 4 of the master port follows the RTS signal level found on the active slave port.
Pinouts
All ports on the 232PTC are configured as RS-232 DCE ports, using DB25 female connectors. Note that a null-modem
type connection will be required to connect the 232PTC to other DCE configured ports. Tables 1 and 2 and Figure 1 show
the configuration of each port.
Bar Code
Port 2
Slave
Terminal
232PTC
Port 1
Scanner
Master
Port
Host
Computer
Slave
Figure 1: Application Example
Table 1
Table 2
Master Port Pinouts
Slave Port Pinouts
Signal Pin
Direction
Signal Pin
Direction
TD 2
Input
TD 2
Input
RD 3
Output
RD 3
Output
RTS 4
Output
RTS 4 Input
GND 7 --------
CTS 5 Output
12VDC 9 --------
GND 7 --------
12VDC
9
--------
5VDC
16
--------
Documentation Number 232PTC3401 - pg. 2/2
1996 B&B Electronics -- Revised September 2001
This product designed and manufactured in USA of domestic and imported parts by
12VDC
5VDC
Ground
Control
Circuitry
2
TD
3
CTS
RTS
7
9
16
5
4
TD
RD
Port 1
2
7
RD
3
9
3
CTS
RTS
7
9
16
5
4
Port 2
Master
Port
RTS
4
2
TD
RD
232PTC Port Diagram
In addition to the standard RS-232 signals, DC power is available for use by low power devices connected to the
232PTC. The unregulated 12VDC power is brought out on pin 9 of all three connectors. In addition, a regulated 5VDC is
brought out on pin 16 of the two slave ports. A total of 225mA may be drawn from the 5V supply. A total of 325mA may be
drawn from the 12V supply. The total current drawn from the unit must be less than 325mA.
Important: Do not connect to pin 9 or 16 in your RS-232 cables if the power is not being used.
Cascading Port Combiners
Port combiners can be cascaded by connecting the master port of each successive unit to one of the slave ports of the
preceding unit. Each additional port combiner adds one slave port to the system.
Specifications
Dimensions:
3.01" x 3.40"x 0.58" (76.45mm x 86.36mm x 14.74mm)
Connectors:
(3) DB-25 female, RS-232 DCE configuration
Power Supply:
12VDC 500mA wall transformer (included)
Current Draw:
175mA
5VDC Outputs:
Slave ports pin 16, 225mA max. total output
12VDC Outputs:
Unregulated, all ports pin 9,
325mA max. total output
Operating Temp:
0-50
C
Signals:
TD, RD, RTS (slave to master only)
CTS indicates open channel (slave only)
DECLARATION OF CONFORMITY
Manufacturer's Name:
B&B Electronics Manufacturing Company
Manufacturer's Address:
P.O. Box 1040
707 Dayton Road
Ottawa, IL 61350 USA
Model Numbers:
232PTC
Description:
RS-232 Two Port Combiner
Type:
Light industrial ITE equipment
Application of Council Directive:
89/336/EEC
Standards: EN
50082-1:1998
EN 50082-1 IEC 801(-3, -4)
EN 61000 -4 (-2, -3, -4, -6)
Michael J. Fahrion, Director of Engineering
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