Description

Emerald-MM-Opto provides an integrated, rugged, and reliable solution for PC/104-expandable embedded systems requiring serial communications in demanding applications. It offers 2 or 4 optically isolated serial ports with RS-232, RS-422, and RS-485 protocols, as well as 24 digital I/O lines, all on a single board.

Optical isolation of 1000V DC or AC protects your embedded system from ground differentials or noise spikes that would damage non-isolated boards. Each port is isolated from the other ports as well as the system. Extended temperature capability (-40 to +85ºC) enables the board to operate in vehicles such as trains and buses without concern for temperature swings. These features enable Emerald-MM-Opto to provide reliable serial communications in harsh environments such as trains and buses.

In addition to ruggedness, Emerald-MM-Opto offers flexibility and advanced features. Each serial port is independently configurable for protocol and IRQ settings. Eight different I/O address combinations are built in. The 16C2850 UART chips with 128-byte FIFOs support high-speed data rates at up to 460kbps without overloading the system processor. Auto-flow control enables easy RS-485 operation by automatically enabling and disabling the transmitter during data transmission, to prevent bus conflicts or excessive software overhead.

Emerald-MM-Opto also offers multiple termination methods on the serial ports to support varying interface requirements. In RS-422 or RS-485 networks, termination resistors are normally installed at the endpoints of the cables to minimize reflections on the lines. The board provides jumper-selectable termination and pull-up/pull-down resistors for this purpose. The sensible jumper positioning and layout help simplify board configuration and minimize confusion.

The 24 digital I/O lines are based on an 82C55 chip and feature programmable direction in 4- and 8-bit groups. All I/O lines contain user-configurable 10K Ohm pull-up resistors for convenience. This 2-in-1 combination of serial ports and digital I/O can help lower the size and cost of your embedded system by eliminating one additional board from your PC/104 stack.

Diamond Systems offers appropriate mating cables for your convenience. Cable no. C-DB9M-1 provides a DB-9 male connector with standard PC serial port pinout. Each serial port requires one cable. Cable no. C-26-18 is a 26-conductor ribbon cable for the digital I/O lines.

System Block Diagram

Configuration

The following I/O addresses are selected with jumpers or 0-ohm resistors. All addresses are in hex.

The interrupt status register indicates the pending interrupt status of all 4 serial ports. It is a read-only register. Only bits 3-0 are used. Bits 7-4 read back as 0 always.