Serial Ports - Epson CW3S16 Operation Manual

Note
Your computer is referred to as a "16-bit" computer. This
system can address over 16M-bytes of memory. In order to
address this much RAM, the internal data communications
in this computer use 16 parallel data lines.

Serial Ports

There are two basic kinds of general purpose l/O (Input/Output)
port. One kind is a "serial" port, where data bits are sent one
at a time along a single wire, in series. Additional wires are
used to send control signals between the transmitting and
receiving devices. These control signals allow the two
communicating devices to determine which of them will send
or receive the data, and when the first bit of a particular byte is
being sent, among other things.
Standardized "protocols" for these signals have been agreed
upon by the microcomputer industry so that the different
manufacturer's machines can communicate with each other.
Your computer system uses the "RS-232C" asynchronous serial
communications interface. The serial port connector is the
left-hand 9-pin "D-type" connector mounted on the system
motherboard.
Electrical information for the serial port is in Appendix A,
"Specifications." For details on the serial port pin connections,
see Appendix D, "Connector Pinouts."
MS-DOS uses labels to refer to the various I/O ports on your
computer. The RS-232C serial ports are assigned the "COM1"
(Communications port #l) and "COM2'" (Communications port
#2) label.
Expanding Your System
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