5
:
: MS-DOS .
:
, . .
. . .
- 1. START . , , . P, . , ( ) .
STOP, . 1 .
, . , , .
- . .
. - . / , .
- (bps). .
. , ( ) , .
, 4, 8 . .
UART
Intel 8250 , 16450, 16550, 16550A. - (UART - Universal Asynchronous Receiver Transmitter). , /.
8250 . , . .
|
|
|
.
, UART .
BIOS . BIOS 0000:0400h.
COM1 3F8h 3F8h 3FFh, COM2 2F8h 2F8h...2FFh.
:
COM1 - IRQ4 ( INT 0Ch);
COM2 - IRQ3 ( INT 0Bh)
3F8h
3F8h . . 3F8h.
, 3FBh, 3F8h . , . , .
, . 3F9h.
:
3F9h
3F9h ( 3F9h ) .
:
| , | |
| BREAK | |
| RS232-C (CTS, DSR, RI, DCD) | |
| 4-7 | , 0 |
3FAh
3FAh . , .
:
| 1 - , | |
| 1-2 | 00 - , , "BREAK". 3FDh; 01 - . 3F8h; 10 - . , 3F8h; 11 - . CTS, RI, DCD, DSR. 3FEh |
| 3-7 | 0 |
|
|
|
3FBh
3FBh , .
:
| 0-1 | : 00 - 5 ; 01 - 6 ; 10 - 7 ; 11 - 8 |
| : 0 - 1 ; 1 - 2 | |
| 3-4 | : X0 - ; 01 - ; 11 - |
| . 0 ( 3-4 11) 1 ( 3-4 01) | |
| . BREAK | |
| 1 - 3F8h 3F9h ; 0 - |
3FCh
3FCh . DTR, RTS, , OUT1 OUT2, .
:
| DTR | |
| RTS | |
| OUT1 () | |
| OUT2 () | |
| , | |
| 5-7 | 0 |
3FDh
3FDh .
:
| . | |
| . , . | |
| . | |
| BREAK: | |
| , | |
| . | |
3FEh
3FEh .
| CTS | |
| DSR | |
| RI | |
| DCD | |
| CTS | |
| DSR | |
| RI | |
| DCD |
BIOS
BIOS, , COM1 COM2. INT 14h.
