Compaq Deskpro Workstation AP230 - Table 5-9. Serial Interfacec

Chapter 5 Input/Output Interfaces
5-10 Compaq Deskpro Personal Computers
Third Edition – April 2001
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 5-9.
Table 5–9. Serial Interface Control Registers
Table 5-9.
Serial Interface Control Registers
COM1
Addr.
COM2
Addr. Register R/W
3F8h 2F8h Receive Data Buffer
Transmit Data Buffer
Baud Rate Divisor Register 0 (when bit 7 of Line Control Reg. Is set)
R
W
W
3F9h 2F9h Baud Rate Divisor Register 1 (when bit 7 of Line Control Reg. Is set)
Interrupt Enable Register
W
R/W
3FAh 2FAh Interrupt ID Register
FIFO Control Register
R
W
3FBh 2FBh Line Control Register R/W
3FCh 2FCh Modem Control Register R/W
3FDh 2FDh Line Status Register R
3FEh 2FEh Modem Status R