FEATURES

		RS-232 to RS-422/RS-485 conversion adaptor
		Design for PM-i386XC and PM-i486DX RS-232 I/F

DESCRIPTION

The MK-2285 is a communication interface conversion adapter. It converts the PC's RS-232 interface to RS-422 or RS-485 interface and can be directly installed in the RS-232 connector. The MK-2285 is easy to use and install. It can be installed in Acqutek's PM-i386XC or PM-i486DX CPU card's RS-232 I/F. It can also be installed in any standard RS-232 I/F of an IBM PC and compatible computer system.

MODEL NUMBER

Model No.	Description
MK-2285	RS-232 to RS-422/485 Adapter
MK-422-PS2	RS-232 to RS-422 Adaptor with PS/2 connector for +5V power supply from PC
MK-485-PS2	RS-232 to RS-485 Adaptor with PS/2 connector for +5V power supply from PC

MK-2285

MK-422-PS2 / MK-485-PS2

FUNCTIONAL DESCRIPTION

The MK-2285 is a communication signal conversion adapter. It converts the PC's RS-232 interface to RS-422 or RS-485 interface. The MK-2285 is easy to use. It can be installed in any standard RS-232 I/F of an IBM PC and compatible computer system. RS-232 Interface The RS-232 interface is a very common one to one communication interface I/F. This means that if one station wants to connect to several stations, it requires the same number of RS-232 communication I/F as number of stations. A typical RS-232 I/F has at least 3 signals. These are the Signal Ground, the TX and the RX. The TX sends data from one station to another station. The RX receives data from the transmitting station. RS-422 Interface The RS-422 interface is similar to RS-232 interface except it is designed to be used in harsher environments. The difference between the RS-232 and RS-422 is the electronic signals. The RS-232 uses single-ended signals while the RS-422 uses differential signals. This means the RS-422 can transmit data at longer distances and with more stability than the RS-232 I/F. The RS-422 can be used in much noisier environments. However, like the RS-422, the RS-232 is for one on one communication. This means if a host computer wants to connect to several remote devices, it requires the same number of RS-422 communication lines as remote devices. A typical RS-422 I/F has at least 5 signals. These are the Signal Ground, the TX+, the TX-, the RX+ and the RX-. The TX+ and TX- send data from one device to another. The RX+ and RX- receive data from one device to another. RS-485 Interface The RS-485 I/F is similar to RS-422 I/F except it is a multiple access network. Unlike the RS-422, it uses the same wires to send and receive data. The benefit is : only one RS-485 I/F is required for a multiple station communication network. The RS-485 interface provides an economical solution for multiple station communication without the overhead of a LAN. However, because all data communication uses the same wires (TRX+ and TRX-), one must detect the communication line status first before sending any data. If the line is busy, it means a station is sending data to another station. The user must wait until the communication line is cleared before any message can be sent. A more detailed explanation regarding the multiple access protocol can be found in the next section. A typical RS-485 I/F has at least 3 signals. These are the Single Ground, the TRX+ and the TRX-.

BLOCK DIAGRAM

INSTALLATION

There are three steps to Install the MK-2285 in a PC's RS-232 I/F. Step 1 : Configure MK-2285 Interface The MK-2285 can be configured as RS-232 to RS-422 or RS-232 to RS-485. The MK-2285 is factory set as RS-232 to RS-422. Therefore, if you wish to use the MK-2285 as RS-232 to RS-422 converter, please skip this step. If you wish to configure MK-2285 as RS-232 to RS-485, you have to open the MK-2285 to re-configure the MK-2285. The following is the configuration for RS-422 and RS-485 configurations. Step 2 : Provide MK-2285 power supply The MK-2285 requires a +5V (20 mA) power supply. It can be powered through pin 9 of the RS-232 connector. PM-i386XC/PM-i486XC or PM-i486DX RS-232 I/F If you wish to convert and connect the MK-2285 to the PM-i386XC/PM-i486XC or PM-i486DX all-in-one CPU card, just adjust the jumper setting in the PM-i386XC/PM-i486XC or PM-i486DX CPU card. The PM-i386XC/PM-i486XC and PM-i486DX provide jumpers to change RS-232 I/F pin 9 from RI input signal to +5V power supply. Other RS-232 I/F If the RS-232 I/F you wish to convert and connect to the MK-2285 is a standard PC's RS-232 I/F, you have to make a wire jumper to supply +5V to pin 9 on the RS-232 connector. The standard PC's RS-232 I/F pin 9 is defined as RI (Ring). It is an input singal, therefore, it is O.K. to make a wire jumper to connect it to +5V, You may also purchase MK-422-PS2 or MK-485-PS2 to connect +5V power supply from Personal Computer's PS/2 interface. Step 3 : Connect MK-2285 to RS-232 I/F Connecting the MK-2285 to the PC's RS-232 I/F is simple and easy. Just plug the MK-2285 RS-232 end (9 pin D-type female connector) to the standard RS-232 I/F (9 pin D-type male connector), and then secure two mounting screws.