Specifications

Chapter 3 Hardware
36 Reference Manual ReadyBoard 800
Serial Interfaces (J15A/B, J11A/B)
The ReadyBoard supports 4 independent serial ports, using two separate chips. The Super I/O controller
(W83627HF) provides Serial ports 1 and 2 through the Serial A DB9 connectors (J15A/B) and the
Southbridge (82801DBM) provides serial ports 3 and 4 through Serial B connector (J11A/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
• Serial A supports ports 1 and 2 using the Super I/O Controller
• Serial Port 1 (COM1) supports RS-232 and full modem support
• Serial Port 2 (COM2) supports RS-232, and full modem support
• Serial B supports ports 3 and 4 using the Southbridge
• Serial Port 3 (COM3) supports RS-232/RS-485/RS-422 and full modem support
• Serial Port 4 (COM4) supports RS-232/RS-485/RS-422 and modem support
NOTE The RS-232/RS-485/RS-422 modes are selected in BIOS Setup
under BIOS and Hardware Settings screen for Serial ports 3 (COM3)
and 4 (COM4). However, the RS-232 mode is the default (Standard)
for any serial port.
RS-485 mode termination is selected with jumper JP5, pins 1-2
(COM3), and pins 3-4 (COM4), when the RS-485 mode is selected
in BIOS Setup. Refer to Table 2-3 for more information.
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 (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 3 as shown in Figure 3-1. Refer also to the following tables for the
specific pins for the other ports and connectors. The RS-422 mode uses a four-wire interface and does
not need any pins tied together, but you must select RS-485 in BIOS Setup.
RB800RS485Cona
Serial B Interface (J11)
for Serial Port 3
(or COM3 Port)
1
2
3
4
5
6
7
8
9
10
20
19
Top View
Standard DB9 Serial
Port Connector (Female)
Rear View
Or
5
4
3
2
1
9
8
7
6
Figure 3-1. RS-485 Serial Port Implementation
Tables 3-8 and 3-9 list the pins and corresponding signals for the Serial A interface connector (J15A/B,
Serial Ports 1 and 2) and Table 3-10 list the pins and corresponding signals for the Serial B interface
connector (J11A/B, Serial Ports 3 and 4). Both serial A DB9 connectors use 9-pin consecutive (1, 6)
and the Serial B connector uses 10-pins, 2 rows, odd/even (1, 2) with 2 mm pin spacing as shown in
Figure 3-1.