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Chapter 5: Technical Description
The DUAL232/AT: utilizes the 16550 UART. This chip features programmable baud rate, data
format, interrupt control and a 16 byte input and output FIFO.
Features Include:
•
Addressable as COM1: or COM2: or fourteen other pre-selected address options
•
"PAL" option allows for unique OEM address selection
•
"Shareable" IRQs allow more than one port to share a single IRQ
•
IRQ's 2-5, 7, 10-12, 15 supported
•
16550 buffered UARTs Standard
•
16 Bit address decode allows for easier integration
The DUAL232/AT: meets the RS-232C specifications and provides an asynchronous serial I/O
port for a modem, plotter, serial printer or serial mouse. This is the standard port configuration
found on the IBM "AT" computer including the DB-9 style connector.
(J1 is for Port 1, J2 is for Port 2)
All modem control signals are implemented on the DUAL232/AT:. If your software requires cer-
tain handshaking signals to be active, then you must connect them either to the device with which
you are communicating or if they are not present in your cable or the device you are communicat-
ing with does not support them, you can satisfy the handshake signal requirements by connecting
pins 7 to 8 (RTS to CTS) and pins 4 to 6 to 1 (DTR to DSR & DCD). Make these connections on
the DB-9 connector that connects to each port. Please refer to Figure 4 for aid in making these
connections.
Manual Number: 00750-010-3
Table 5-1: J1 & J2 RS-232 Connector Pin-Outs:
Name
TD Transmit Data
RTS Request To Send
DTR Data Term Ready
GND Ground
RD Receive Data
DCD Data Carrier Detect
DSR Data Set Ready
CTS Clear To Send
RI Ring Indicator
Pin #
Mode
3
Output RS-232
7
Output RS-232
4
Output RS-232
5
2
Input RS-232
1
Input RS-232
6
Input RS-232
8
Input RS-232
9
Input RS-232
Page 11
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