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Chapter 5 Input/Output Interfaces
5-6 Compaq iPAQ Family of Internet Devices
First Edition – March 2000
5.4.2 SERIAL TEST INTERFACE
Legacy-free systems do not provide an externally accessible serial port but do include a serial
header connector on the system board to satisfy some the requirements of some operating
systems. The test header and pinout is shown in the following figure:
Figure 5-4.
Serial Interface Header (on legacy-free system board)
5.4.3 SERIAL INTERFACE PROGRAMMING
Programming the serial interfaces consists of configuration, which occurs during POST, and
control, which occurs during runtime.
5.4.3.1 Serial Interface Configuration
The serial interface must be configured for a specific address range (COM1, COM2, etc.) and
also must be activated before it can be used. Address selection and activation of the serial
interface are affected through the PnP configuration registers of the LPC47B277 I/O controller.
The serial interface configuration registers are listed in the following table:
Table 5–6
. Serial Interface Configuration Registers
Table 5-6.
Serial Interface Configuration Registers
Index
Address Function R/W
30h Activate R/W
60h Base Address MSB R/W
61h Base Address LSB R/W
70h Interrupt Select R/W
F0h Mode Register R/W
NOTE:
Refer to LPC47B277 data sheet for detailed register information.
5.4.3.2 Serial Interface Control
The BIOS function INT 14 provides basic control of the serial interface. The serial interface can
be directly controlled by software through the I/O-mapped registers listed in Table 5-7.
TX Data 5
CD 1
DTR 7
Gnd 9
RX Data 3
2 DSR
6 CTS
8 RI
4 RTS