Com part datasheet 詳細資料－勇ㄅㄟㄅㄟ胡言亂語堂

The standard port adresses are given below. Most PCs have them. If you are using IBM PS/2, equipped with a micro-channel bus, different addresses and interrupt requests can be expected. Just like LPT ports, base adresses for ��-ports can be obtained from the data range in BIOS.

Name	Address	IRQ
COM 1	3F8	4
COM 2	2F8	3
COM 3	3E8	4
COM 4	2E8	3

Standard Port Addresses

The table below contains the address having the addresses for COM-ports in BIOS data range. Each address has two bytes.

Start Address	Function
0000:0400	COM1's Base Address
0000:0402	COM2's Base Address
0000:0404	COM3's Base Address
0000:0406	COM4's Base Address

COM Port Addresses in the BIOS Data Area

3F8 offset 總覽

Table of Registers

Base Address	DLAB	Read/Write	Abr.	Register Name
+ 0	=0	Write	-	Transmitter Holding Buffer
	=0	Read	-	Receiver Buffer
	=1	Read/Write	-	Divisor Latch Low Byte
+ 1	=0	Read/Write	IER	Interrupt Enable Register
+ 1	=1	Read/Write	-	Divisor Latch High Byte
+ 2	-	Read	IIR	Interrupt Identification Register
+ 2	-	Write	FCR	FIFO Control Register
+ 3	-	Read/Write	LCR	Line Control Register
+ 4	-	Read/Write	MCR	Modem Control Register
+ 5	-	Read	LSR	Line Status Register
+ 6	-	Read	MSR	Modem Status Register
+ 7	-	Read/Write	-	Scratch Register

3F8

Below is the table with some standard rates and their divisor latch high bytes & low bytes.

Speed (BPS)	Divisor (Dec)	Divisor Latch High Byte	Divisor Latch Low Byte
50	2304	09h	00h
300	384	01h	80h
600	192	00h	C0h
2400	48	00h	30h
4800	24	00h	18h
9600	12	00h	0Ch
19200	6	00h	06h
38400	3	00h	03h
57600	2	00h	02h
115200	1	00h	01h

Table of Commonly Used Baudrate Divisors

3F9

Bit	Notes
Bit 7	Reserved
Bit 6	Reserved
Bit 5	Enables Low Power Mode (16750)
Bit 4	Enables Sleep Mode (16750)
Bit 3	Enable Modem Status Interrupt
Bit 2	Enable Receiver Line Status Interrupt
Bit 1	Enable Transmitter Holding Register Empty Interrupt
Bit 0	Enable Received Data Available Interrupt

Interrupt Enable Register

http://www.cs.ucv.ro/staff/dtusaliu/DC/uart.html

http://www.lookrs232.com/rs232/addresses.htm

http://www.eng.usf.edu/~gilbert/courses/modelandanalysis/notes/serialtransmit/8250/8250manuals/baudrate.pdf

http://www.quicklogic.com/assets/pdf/data_sheets/QL_UART_PSB_DS_RevC.pdf

http://retired.beyondlogic.org/serial/serial.htm#8

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勇ㄅㄟㄅㄟ胡言亂語堂

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