BAMHC

BAMHC Datasheet

BAMHC0812 pg. 1/3

Part	Datasheet
BAMHC	BAMHC (pdf)

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B&B ELECTRONICS BAMHC0812 pg. 1/3 RS-232, 422 or 485 Buffered Asynchronous Modem Handshake Controller Model BAMHC Description The BAMHC provides hardware handshake control for Radio Frequency and other modems requiring the RTS line to control the transmitter. RS-232, RS-422, or RS-485 data signals at up to 19.2K bps are supported. The BAMHC raises RTS and buffers up to 160 characters while waiting for the modem to be ready to transmit. The amount of time data is buffered is userselectable for 5, 10, or 50 ms. Alternatively, the modem’s CTS line can be used to indicate ready to transmit. The BAMHC supports both the Transmit and Receive data lines, and the built-in microprocessor provides hardware control of the RS-422/485 driver. The BAMHC enables the driver when it first sees data from the modem. It waits 10 bits after transmission is complete, then disables the RS-422/485 driver. All connections to the host device are provided on the same DB-25 female connector, while RS-232 modem connections are to a DB25 male. The unit is powered by 12 VDC and requires a maximum of 65 mA. RS-232 Host Connections Connection of the BAMHC is simple and straightforward. The DB-25 female serial connector is used for connecting to either RS-232, RS-422 or RS-485. The RS-232 signals are pinned as a DCE device input on Pin 2 and output on Pin This means that a straight through cable can be used from your DB-25 port from any DTE device such as a PC or terminal. A standard 9 to 25 pin adapter can be used in cases where the serial port on the DTE device is a DB-9. For connecting to modems or other DCE devices, a null modem cable or adapter that swaps pins 2 & 3 is needed. See Figure 1 for connection diagrams to 9 pin and 25 pin DTE and DCE devices. Note that because RS-422 and RS-485 signals are also available on the same connector, special care should be taken not to hook any external signals to these pins. This should not be a problem for most serial devices, but if your device has power or special non-standard outputs, a custom cable should be made that does not connect to the extra pins on the DB-25 connector. CTS is provided as an output on pin 5 to tell the host device when buffer space is available in the BAMHC. Figure 1 RS-232 Host Connection Diagrams DB25 DTE Device BAMHC DB25S DB25 DCE Device BAMHC DB25S Signal GND 7 5 CTS 4 RTS DCD 8 7 Signal GND 7 DB9 DTE Device BAMHC DB25S Signal GND 7 DB9 DCE Device BAMHC DB25S 5 CTS 4 RTS DSR 6 DCD 8 Signal GND 7 PRODUCT INFORMATION International Office 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax 433-5104 European Office Westlink Commercial Park Oranmore Co. Galway Ireland +353 91 792444 Fax +353 91 792445 B&B ELECTRONICS BAMHC0812 pg. 2/3 RS-422 & RS-485 Host Connections The RS-422/485 driver and receiver are connected to 4 pins on the DB-25 female connector. Signal ground is still on Pin When connecting to a four-wire RS-422/485 device or system, connect the output of your device to pins 16 + and 17 Input to your device should be connected to pins 14 + and 15 For two-wire RS-485 systems, the driver and receiver of the BAMHC must be connected together by tying pins 14 and 16 together and 15 and 17 together. This allows the BAMHC to communicate half-duplex over the same pair. Refer to Figure 2 for connection diagrams to RS-422 or RS-485 equipment. If termination is needed, a space on the PC board of the BAMHC labeled R6 allows you to solder in a termination resistor across the RD A and RD B lines. The off-state bias resistor values can also be changed by removing R5 and R8 and replacing them with through-hole components. Before making modifications to the BAMHC, be sure to consult the B&B Electronics RS-422/485 Application Note or other sources of information to see if termination is necessary. The Application Note is available from our Web site, or call and we will be happy to send one at no charge. Figure 2 RS-422/485 Host Connection Diagrams 422/485 4W Device BAMHC DB25S 485 2 Wire Device BAMHC DB25S TD A - TD B + RD A - RD B + 17 RD A 16 RD B 15 TD A 14 TD B

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B&B ELECTRONICS

BAMHC0812 pg. 1/3

RS-232, 422 or 485 Buffered Asynchronous

Modem Handshake Controller

Model BAMHC

Description The BAMHC provides hardware handshake control for Radio

Frequency and other modems requiring the RTS line to control the transmitter. RS-232, RS-422, or RS-485 data signals at up to 19.2K bps are supported. The BAMHC raises RTS and buffers up to 160 characters while waiting for the modem to be ready to transmit. The amount of time data is buffered is userselectable for 5, 10, or 50 ms. Alternatively, the modem’s CTS line can be used to indicate ready to transmit.

The BAMHC supports both the Transmit and Receive data lines, and the built-in microprocessor provides hardware control of the RS-422/485 driver. The BAMHC enables the driver when it first sees data from the modem. It waits 10 bits after transmission is complete, then disables the RS-422/485 driver. All connections to the host device are provided on the same DB-25 female connector, while RS-232 modem connections are to a DB25 male. The unit is powered by 12 VDC and requires a maximum of 65 mA.

RS-232 Host Connections Connection of the BAMHC is simple and straightforward. The DB-25 female serial connector is used for
connecting to either RS-232, RS-422 or RS-485. The RS-232 signals are pinned as a DCE device input on Pin 2 and output on Pin This means that a straight through cable can be used from your DB-25 port from any DTE device such as a PC or terminal. A standard 9 to 25 pin adapter can be used in cases where the serial port on the DTE device is a DB-9. For connecting to modems or other DCE devices, a null modem cable or adapter that swaps pins 2 & 3 is needed. See Figure 1 for connection diagrams to 9 pin and 25 pin DTE and DCE devices. Note that because RS-422 and RS-485 signals are also available on the same connector, special care should be taken not to hook any external signals to these pins. This should not be a problem for most serial devices, but if your device has power or special non-standard outputs, a custom cable should be made that does not connect to the extra pins on the DB-25 connector. CTS is provided as an output on pin 5 to tell the host device when buffer space is available in the BAMHC.

Figure 1 RS-232 Host Connection Diagrams

DB25 DTE Device

BAMHC DB25S

DB25 DCE Device

BAMHC DB25S

Signal GND 7
5 CTS
4 RTS

DCD 8
7 Signal GND 7

DB9 DTE Device

BAMHC DB25S

Signal GND 7

DB9 DCE Device

BAMHC DB25S
5 CTS
4 RTS

DSR 6

DCD 8

Signal GND 7

PRODUCT INFORMATION

International Office 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax 433-5104 European Office Westlink Commercial Park Oranmore Co. Galway Ireland +353 91 792444 Fax +353 91 792445

B&B ELECTRONICS

BAMHC0812 pg. 2/3

RS-422 & RS-485 Host Connections The RS-422/485 driver and receiver are connected to 4 pins on the DB-25 female connector. Signal ground is still on Pin When connecting to a four-wire RS-422/485 device or system, connect the output of your device to pins 16 + and 17 Input to your device should be connected to pins 14 + and 15 For two-wire RS-485 systems, the driver and receiver of the BAMHC must be connected together by tying pins 14 and 16 together and 15 and 17 together. This allows the BAMHC to communicate half-duplex over the same pair. Refer to Figure 2 for connection diagrams to RS-422 or RS-485 equipment. If termination is needed, a space on the PC board of the BAMHC labeled R6 allows you to solder in a termination resistor across the RD A and RD B lines. The off-state bias resistor values can also be changed by removing R5 and R8 and replacing them with through-hole components. Before making modifications to the BAMHC, be sure to consult the B&B Electronics RS-422/485 Application Note or other sources of information to see if termination is necessary. The Application Note is available from our Web site, or call and we will be happy to send one at no charge.

Figure 2 RS-422/485 Host Connection Diagrams
422/485 4W Device

BAMHC DB25S
485 2 Wire Device BAMHC DB25S

TD A - TD B + RD A - RD B +
17 RD A 16 RD B 15 TD A 14 TD B

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Datasheet ID: BAMHC 521494