Serial Interfaces (J11, J13); Figure 3-1. Rs485 Serial Port Implementation - Ampro Little Board 700 Reference Manual

Chapter 3
Pin # Signal
24 GND
25 SLCT
26 GND
Notes: The shaded area denotes power or ground. The signals marked with * = Negative true logic.

Serial Interfaces (J11, J13)

Two chips provide the circuitry for the 4 serial ports. The VT86C686B provides serial ports 1 and 2
through connector J11 and the Super I/O provides serial ports 3 and 4 through connector J13. The four
serial ports support the following features:
•
Four individual 16550-compatible UARTs
•
Programmable word length, stop bits and parity
•
16-bit programmable baud rate generator
•
Interrupt generator
•
Loop-back mode
•
Four individual 16-bit FIFOs
• Serial A Interface (J11)
♦
Serial Port 1 (COM1) supports RS232/RS485/RS422 and full modem support
♦
Serial Port 2 (COM2) supports RS232/RS485/RS422, and IrDA
• Serial B Interface (J13)
♦
Serial Port 3 (COM3) supports RS232/RS485/RS422 and full modem support
♦
Serial Port 4 (COM4) supports RS232/RS485/RS422
NOTE The RS232 and RS485/RS422 modes can be selected for any serial port in
BIOS Setup under the Integrated Peripherals screen. However, the RS232
mode is the default selection (Standard) for any serial port.
To implement the RS485 mode on any serial port, you must tie the equivalent pins together for each
port. For example; on Serial Port 1, tie pin 3 to 5 and pin 4 to 6 at the Serial A interface connector (J11)
as shown in Figure 3-1. As an alternate, tie pin 2 to 3 and pin 7 to 8 at the DB9 serial connector for
Serial Port 1 as shown in Figure 3-1. Refer also to the following tables for the specific pins for the other
ports on each connector. The RS422 mode uses a four-wire interface and does not need any pins tied
together, but you must select RS485 in BIOS Setup.
Serial A Interface (J11)
for Serial Port 1
(or COM1 Port)
Top View
Table 3-14 gives the pins and corresponding signals for the Serial A interface connector (Serial Ports 1
and 2) and Table 3-15 gives the pins and corresponding signals for the Serial B interface connector
(Serial Ports 3 and 4).
40
In/Out Description
Digital Ground
In Select – This is a status output signal from the printer. A High
State indicates it is selected and powered on.
Digital Ground
19 9 5 3 1
7
10 8 6
20 4 2

Figure 3-1. RS485 Serial Port Implementation

Reference Manual
Standard DB9 Serial
Or
Port Connector (Female)
Rear View
Hardware
1 2 3 4 5
6 7 8 9
LittleBoard 700