Users’ Manual
EDI-53 Series Digital Indicator
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6
RS-232C SERIAL INTERFACE
EDI-53 Indicator is provided with a RS-232C serial communication interface. The serial communication
interface is used by the EDI-53 indicator to transfer logged data or setup data directly to a computer
without operator intervention.
The PRINT feature also uses the serial interface to send logged data or setup data to a serial printer. Any
printer with a RS-232C serial interface can be used to print logged data from the EDI-53 Indicator.
The following sections describe the operation of the serial interface for use both with a computer and a
printer.
6.1
Interfacing to a Computer or a Printer
The RS-232C serial interface in the EDI-53 Indicator employs a subset of the EIA standard RS-232C
standard. A special interface cable for connecting the indicator serial port to a standard IBM PC/AT
compatible computer with a 9 pin serial port is supplied with the indicator. This serial interface cable
should also connect to serial ports of most commercially available printers using a 9-pin to 25 pin
converter, if required.
The interface cable consists of a 7 pin circular connector for connecting to the indicator at one end and a
9-pin D shell sub-miniature connector for connecting to a Personal Computer at the other end.
It is assumed that the serial port of the users computer follows the IBM PC/AT convention. An
intermediate patch cord will be necessary if this condition is not true. In such cases please contact factory
for more information.
6.2
Serial Interface Specifications
Transmission Mode:
Asynchronous, Full duplex
Baud rate:
2400 (Default)
Serial Data Format:
1 Start bit, 8 data bits, No parity, 1 stop bit.
The format of serial data consists of a start bit, data bits, no parity bit, and a stop bit. The output is in a
mark state when not in transmission. The data bits start with the least significant bit (LSB).
Signal levels:
-3 V or more for a mark condition (logical 1)
+3 V or more for a space condition (logical 0)
Input/Output circuit:
A Maxim 'MAX 232' or equivalent IC is used as the line driver (output) and receiver (input) and TTL to
RS-232C level converter.
Connector (Indicator side):
7-pin weather proof circular bayonet latching connector. Manufacturer & Part # Amphenol 621N-16F-10-
7S.
Connector (Computer side):
9-pin D-sub miniature, Female, O/E/N type DE 09 S or equivalent connector that conforms to EIA RS-
