Rev 007, 04/12 33
© SP Scientific 2012
EDC Programmer’s Reference
Overview
The MPC and EDC controllers are used in a variety of cooling products manufactured
by SP Scientific. The commands used by a specific system will vary per the
descriptions at the end of this reference, but the operational aspects, hardware and
software of the interface are consistent across the product line. This document details
the communications interface between the microcontroller and the independent
intelligent host processor.
See the end of this section for a sample program that will execute on an IBM-
compatible PC within either GWBASIC or QBASIC. It is suggested, should initial
attempts to communicate be unsuccessful, that this program be tried. It is as
straightforward as a program may be and will aid in locating the source of difficulty: if
this program runs successfully, then the difficulty must be due to one of the “extras” or
“features” of the unsuccessful driver.
Hardware
The hardware of the RS 232 interface meets or exceeds the specifications of EIA
standard RS 232 E 1991, with regard to electrical characteristics (impedance, open
circuit characteristics, voltages, etc.).
The physical interface connector is a 9 position female D subminiature connector, with
pin-out as specified by the IBM Corporation for the "PC AT" [COM1] communication
port.
The connections used within the interface will be limited to:
GND Signal Ground
TXD Transmit Data
RXD Receive Data
RTS Request to Send
CTS Clear to Send
DTR Data Terminal Ready
DSR Data Set Ready
The pinout for a fully wired null modem cable is:
2-3, 3-2, 4-4, 5-5, 6-7, 7-6, 8-8
All other signals of the RS 232 standard are immaterial to this application, or
terminated, as appropriate.
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