0623 Roselle Street, San Diego, CA 92121 • (858) 550-9559 • FAX (858) 550-7322 contactus@accesio.com • www.accesio.com MODEL PCI-ICM422(485)/2(4) USER MANUAL FILE: MPCI-ICM4S.
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Table of Contents Chapter 1: Introduction..................................................................................................................................... 5 Specifications................................................................................................................................................. 7 Figure 1-1: 422 Block Diagram(Only one serial channel shown)................................................................ 8 Figure 1-2: 485 Block Diagram ................
Chapter 1: Introduction These cards provide effective asynchronous serial communications in RS422 and RS485 networks on long communications lines in noisy environments. The cards feature independent serial ports and use type 16550 buffered UARTs. The data lines are opto-isolated from the computer and from each other to assure communication through large common mode noise. Both the RS422 and RS485 cards are 12.
Communication Mode The 422 models support Full-Duplex and Half-Duplex communications with a 4-wire cable connection. 485 models support Half-Duplex communications with a 2-wire cable connection. HalfDuplex allows traffic to travel in both directions, but only one way at a time. RS485 communications commonly use the Half-Duplex mode since they share only a single pair of wires and installation cost is reduced.
Specifications Communications Interface • I/O Connection: 37 Pin DBM connector. • Serial Ports: An external breakout cable that terminates with female D-sub 9-pin connectors. • Character length: 5, 6, 7, or 8 bits. • Parity: Even, odd or none. • Stop Interval: 1, 1.5, or 2 bits. • Serial Data Rates: Up to 115,200 baud, asynchronous, A faster range of rates, up to 460,800 baud, is achieved by jumper selection on the card. A type 16550 buffered UART is used and has FIFO buffer.
DB50M Figure 1-1: 422 Block Diagram(Only one serial channel shown) COMPUTER PCI BUS OSCILLATOR Tx PCI Tx/Rx+ UART 16550 OR SIMILAR INTERFACE CHIP Tx TRANSCEIVER OPTORx ISOLATOR DB37 Tx/Rx- Rx DEVICES IRQ AUTO RTS CIRCUITRY Figure 1-2: 485 Block Diagram 8 Manual PCI-ICM-422(485)/2(4)
Chapter 2: Installation A printed Quick-Start Guide (QSG) is packed with the card for your convenience. If you’ve already performed the steps from the QSG, you may find this chapter to be redundant and may skip forward to begin developing your application. The software provided with this card is on CD and must be installed onto your hard disk prior to use. To do this, perform the following steps as appropriate for your operating system.
Hardware Installation 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Make sure to set switches and jumpers from either the Option Selection section of this manual or from the suggestions of SETUP.EXE. Do not install card into the computer until the software has been fully installed. Turn OFF computer power AND unplug AC power from the system. Remove the computer cover. Carefully install the card in an available 5V or 3.3V PCI expansion slot (you may need to remove a backplate first).
Chapter 3: Option Selection To help you locate the jumpers described in this section, refer to the Option Selection Map at the end of this chapter. Operation is determined by jumper installation as described in the following paragraphs. Tx+/R x+ COM422LD 120 0.1 :F Tx-/R xFigure 3-1: Simplified Termination Schematic Terminations A transmission line should be terminated at the receiving end in its characteristic impedance.
Serial2 subkey: PortAddress = REG_DWORD 0xFC00 Interrupt = REG_WORD 5 DosDevices = REG_SZ COM3 InterruptStatus = REG_DWORD 0xFC08 PortIndex = REG_DWORD 1 Indexed =0 Serial3 subkey: PortAddress = REG_DWORD 0xFD00 Interrupt = REG_DWORD 5 DosDevices = REG_SZ COM4 InterruptStatus = REG_DWORD 0xFCO8 PortIndex = REG_DWORD 2 Indexed=0 Serial4 subkey: PortAddress = REG_DWORD 0xFD80 Interrupt = REG_DWORD 5 DosDevices = REG_SZ COM5 InterruptStatus = REG_DWORD 0xFC08 PortIndex - REG_DWORD 3 Indexed=0 Serial5 subkey:
LDO COM C LOA D (OUTPUT) LDI LDI COM C LOA D (INPUT) COM B LOAD (INPUT) COM A LOAD (INPUT) LDO COM D LOAD (OUTPUT) LDI COM D LOAD (INPUT) x1 x4 COM B x1 x4 COM C x1 x4 COM D x1 x4 BAUD SOURCE JUMP ERS COM A Manual PCI-ICM-422(485)/2(4) 13 LDO LDI COM B LOA D (OUTPUT) LDO COM A LOA D (OUTPUT) Figure 3-2: Option Selection Map
Chapter 4: Address Selection The cards use four separate address spaces. COM A occupies 16 consecutive address locations and COM B, COM C, and COM D each occupy eight consecutive register locations. The two-port versions of these cards do not have ports COM C and COM D. PCI architecture is Plug-and-Play. This means that the BIOS or Operating System determines the resources assigned to PCI cards rather than you selecting those resources with switches or jumpers.
Chapter 5: Programming There are sample programs provided with the card in C, Pascal, QuickBASIC, and several Windows languages. DOS samples are located in the DOS directory and Windows samples are located in the WIN32 directory. Initialization Initializing the chip requires knowledge of the UART's register set. The first step is to set the baud rate divisor. You do this by first setting the DLAB (Divisor Latch Access Bit) high. This bit is Bit 7 at Base Address +3.
The second initializing step is to set the Line Control Register at Base Address +3. This register defines word length, stop bits, parity, and the DLAB. Bits 0 and 1 control word length and allow word lengths from 5 to 8 bits. Bit settings are extracted by subtracting 5 from the desired word length. Bit 2 determines the number of stop bits. There can be either one or two stop bits. If Bit 2 is set to 0, there will be one stop bit. If Bit 2 is set to 1, there will be two.
Transmission RS485 transmission is simple to implement. The AUTO feature of the 422/485 cards automatically enables the transmitter when data are ready to send. No software enabling is required.
Chapter 6: Connector Pin Assignments A breakout cable is delivered with each card. The cable mates with a 37-pin connector on the card mounting bracket and, at the other ends of the cable, the popular 9-pin D sub-miniature male connector is used to interface with your communication lines. Those connectors are equipped with 440 threaded standoffs (female screw lock) to provide strain relief.
Appendix A: Application Considerations Introduction Working with RS422 and RS485 devices is not much different from working with standard RS232 serial devices and these two standards overcome deficiencies in the RS232 standard. First, the cable length between two RS232 devices must be short; less than 50 feet at 9600 baud. Second, many RS232 errors are the result of noise induced on the cables.
A maximum common mode voltage rating of +7V provides good noise immunity from voltages induced on the twisted pair lines. The signal ground line connection is necessary in order to keep the common mode voltage within that range. The circuit may operate without the ground connection but may not be reliable. Parameter Conditions Driver Output Voltage (unloaded) Driver Output Voltage (loaded) Min. Max.
Figure A-1: Typical RS485 Two-Wire Multidrop Network RS485 Four-Wire Multidrop Network An RS485 network can also be connected in a four-wire mode. In a four-wire network it's necessary that one node be a master node and all others be slaves. The network is connected so that the master communicates to all slaves and all slaves communicate only with the master. This has advantages in equipment that uses mixed protocol communications.
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