Serial Interface Programming; Table; Table 5-8. Serial Interfacec; Table 5-9. Serial Interfacec - HP Deskpro EX Technical Reference Manual

5.4.2 SERIAL INTERFACE PROGRAMMING

Programming the serial interfaces consists of configuration, which occurs during POST, and
control, which occurs during runtime.
5.4.2.1 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 LPC47B357 I/O controller.
The serial interface configuration registers are listed in the following table:
Table 5–8. Serial Interface Configuration Registers
Serial Interface Configuration Registers
Index
Address Function
30h Activate
60h Base Address MSB
61h Base Address LSB
70h Interrupt Select
F0h Mode Register
NOTE:
Refer to LPC47B357 data sheet for detailed register information.
5.4.2.2 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 5-9.
Table 5–9. Serial Interface Control Registers
COM1 COM2
Addr. Addr.
3F8h 2F8h
3F9h 2F9h
3FAh 2FAh
3FBh 2FBh
3FCh 2FCh
3FDh 2FDh
3FEh 2FEh

Table 5-8.

Table 5-9.
Serial Interface Control Registers
Register
Receive Data Buffer
Transmit Data Buffer
Baud Rate Divisor Register 0 (when bit 7 of Line Control Reg. Is set)
Baud Rate Divisor Register 1 (when bit 7 of Line Control Reg. Is set)
Interrupt Enable Register
Interrupt ID Register
FIFO Control Register
Line Control Register
Modem Control Register
Line Status Register
Modem Status
Compaq Deskpro EX Series of Personal Computers
First Edition - August 2000
Technical Reference Guide
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
W
W
W
R/W
R
W
R/W
R/W
R
R
5-9