Crown AMB-5, SMX-6, MPX-6 installation manual RS232 Cable Wiring for a PC

IQ Mixer / Multiplexer Hardware Installation

while it is connected to the Crown Bus, skip ahead to Section 3.2.

There are two main communication standards sup- ported by the unit for serial communication with a host computer. They are RS232 and RS422.

RS232 is commonly used with IBM PCs and com- patibles. Because it uses unbalanced signal wiring, it cannot be used for distances over 50 feet (15.2 m).

RS422 is commonly used with Macintosh comput- ers. It uses balanced signal wiring and can be used for distances up to 2,000 feet (610 m).

Although uncommon, RS423 communication can also be used. It uses the unbalanced transmitter (TXD) wiring of RS232 and the balanced receiver (RXD) wiring of RS422 to provide signal ground isolation between the transmit and receive lines. With a proper cable it can be used over a greater distance than RS232…but a shorter distance than RS422. For details contact either Crown Tech. Sup- port or Amcron Tech. Services (see page 22).

The following illustrations show how to wire the two most common serial cables:

PC (RS232)			SMX-6 (RS232)
1	5	1	13
6	9	14	25

Cable connectors are numbered as they appear from the front.

			PIN	PIN
		Not used	1,4,6,9
ReceiveData (RXD)			2	3	Transmit Data (TXD)
Transmit Data (TXD)			3	2	Receive Data (RXD)
Signal Ground (GND)			5	7	Signal Ground (GND)
Request to Send (RTS)			7	4	Clear to Send (CTS)
Clear to Send (CTS)			8	5	Request to Send (RTS)
		Fig. 3.2 RS232 Cable Wiring for a PC
Macintosh				SMX-6 (RS422)
(RS422)
6	7	8	1		13
3	4	5
	1	2	14		25

Cable connectors are numbered as they appear from the front.

	PIN	PIN
Output handshake	1	4	Clear to Send (CTS)
Input handshake	2	5	Request to Send (RTS)
Transmit data –	3	2	Serial In (–)
Ground	4	7	Signal Ground (GND)
Receive data –	5	3	Serial Out (–)
Transmit data +	6	10	Serial In (+)
Not used	7
Receive data +	8	9	Serial Out (+)

Fig. 3.3 RS422 Cable Wiring for a Macintosh

It is also possible to use RS232 to communicate with a Macintosh computer. Here’s how to wire the cable:

Macintosh				SMX-6 (RS232)
(RS232)
6	7	8	1	13
3	4	5
	1	2	14	25

Cable connectors are numbered as they appear from the front.

	PIN	PIN
Output handshake	1	4	Clear to Send (CTS)
Input handshake	2	5	Request to Send (RTS)
Transmit data –	3	2	Receive Data (RXD)
Ground	4	7	Signal Ground (GND)
Receive data –	5	3	Transmit Data (TXD)
Not used	6,7,8

Fig. 3.4 RS232 Cable Wiring for a Macintosh

Important: Do not use twisted-pair wire for RS232 because it increases crosstalk. Instead use an un- twisted cable or ribbon cable. Twisted-pair wire can be used for RS422.

3.1.1Communication Standards and Parameters Before communication can take place between the unit and a host computer the communication stan- dard must be selected and the communication pa- rameters must be set with switches accessed through an opening in the side of the chassis. (Fig- ures 2.2 and 3.5)

Caution: Be sure to disconnect the AC power from the unit before selecting a different communication standard or changing the parameters.

IBM PC-compatible computers typically have an RS232 serial port, so the communication standard switch should be moved to the right (Figure 3.5). With a Macintosh host computer, the standard is usually RS422, and the communication standard switch should be moved to the left. In the rare event that RS423 communication is used, set the switch to the RS422 position.

Setting the communication parameters for RS232 and RS422 serial communication is accomplished using the six segment baud rate and parity DIP switch in Figure 3.5. The first four switches select the baud rate and the last two set the parity. Use the fastest baud rate possible. The highest baud rate supported by the unit is 19.2 K baud. Parity check- ing is not presently supported and should be OFF. The odd/even parity bit doesn’t matter when parity is switched OFF. The unit has been factory set to 1 stop bit and 8 data bits.

Important: The communication standard and param-

Rev. 0 Page 11