Ampro Corporation 700 manual Serial Interfaces J5A/B, J3A/B, RS485 Serial Port Implementation

Chapter 3 Hardware

Serial Interfaces (J5A/B, J3A/B)

The ReadyBoard supports 4 independent serial ports, using two separate chips. The Southbridge (VT86C686B) provides serial ports 1 and 2 through the Serial A DB9 connector (J5A/B) and the Secondary I/O chip (W83877TF) provides serial ports 3 and 4 through Serial B connector (J3A/B). 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

•Wake on Ring feature

•Serial A supports ports 1 and 2 using the Southbridge/Super I/O

♦Serial Port 1 (COM1) supports RS232 and full modem support

♦Serial Port 2 (COM2) supports RS232, and full modem support

•Serial B supports ports 3 and 4 using the Secondary I/O Controller

♦Serial Port 3 (COM3) supports RS232/RS485/RS422 and full modem support

♦Serial Port 4 (COM4) supports RS232/RS485/RS422 and modem support

NOTE	The RS232/RS485/RS422 modes are selected in BIOS Setup under BIOS
	and Hardware Settings screen for Serial ports 3 (COM3) and 4 (COM4).
	However, the RS232 mode is the default (Standard) for any serial port.
	RS485 mode termination is selected with jumper JP6, pins 1-2 (COM3),
	and pins 3-4 (COM4), when the RS485 mode is selected in BIOS Setup.

To implement the two-wire RS485 mode on either serial port, you must tie the equivalent pins together for each port.

For example; on Serial Port 3, tie pin-3 (RX3-) to -5 (TX3-) and pin-4 (TX3+) to -6 (RX3+) at the Serial B interface connector (J3) 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 3 as shown in Figure 3-1. Refer also to the following tables for the specific pins for the other ports and connectors. The RS422 mode uses a four-wire interface and does not need any pins tied together, but you must select RS485 in BIOS Setup.

	19	9 7 5 3 1	1	2	3	4	5
Serial B Interface (J3)		Or	Standard DB9 Serial
for Serial Port 3			Port Connector (Female)
(or COM3 Port)	20	10 8 6 4 2	Rear View
Top View				6	7	8	9

Figure 3-1. RS485 Serial Port Implementation

RB700RS485ConB

Tables 3-12 and 3-13 list the pins and corresponding signals for the Serial A interface connector (J5A/B, Serial Ports 1 and 2) and Table 3-14 list the pins and corresponding signals for the Serial B interface connector (J3A/B, Serial Ports 3 and 4).

ReadyBoard 700 Reference Manual 39