INT 14H
Encyclopedia
INT 14H, the serial communication interrupt
| AH=00h | init Comm Port |
| AH=01H | Write Character |
| AH=02H | Read Character |
| AH=03H | Status Request |
| AH=04H | Extended Init |
AH=00h—init Comm Port
| Prior to issuing INT 14H | Upon returning from INT 14H | ||||
|---|---|---|---|---|---|
| High | Low | High | Low | ||
| AX | 00h | Comm Parm Byte | AX | Line Status | Modem Modem A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data... Status |
| BX | BX | ||||
| CX | CX | ||||
| DX | Port Number (0=Com 1, 1=Com2, etc.) | DX | |||
| Modem Status Byte—Low Byte | ||||||||
|---|---|---|---|---|---|---|---|---|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Description |
| x | Received Line signal detect | |||||||
| x | Ring Indicator | |||||||
| x | data set Data set A data set is a collection of data, usually presented in tabular form. Each column represents a particular variable. Each row corresponds to a given member of the data set in question. Its values for each of the variables, such as height and weight of an object or values of random numbers. Each... ready |
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| x | clear to send | |||||||
| x | Delta receive line signal detect | |||||||
| x | Trailing edge ring detector | |||||||
| x | delta data set ready | |||||||
| x | Delta clear to send | |||||||
| Line Status Byte | ||||||||
|---|---|---|---|---|---|---|---|---|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Description |
| x | Time-out Unpredictable results in other bits when this bit is set to 1 | |||||||
| x | Transmitter shift register empty | |||||||
| x | Transmitter holding register empty | |||||||
| x | Break detect | |||||||
| x | Framing error Framing error Framing error can refer to the following:*Generally, a framing error is the result of starting to read a sequence of data at the wrong point.*In serial communications, a framing error is the result of reading a string of symbols which are grouped in blocks at the wrong starting point... |
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| x | Parity error | |||||||
| x | Overrun error | |||||||
| x | Data ready | |||||||
| Com Port Parameter Byte | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Description | Allowable Values | ||||||||
| x | x | x | Baud Rate |
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| x | x | Parity |
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| x | Stop Bits | 0=1 stop bit | |||||||||||||||
| x | x | Word length |
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AH=01H—Write Character
| Prior to issuing INT 14H | Upon returning from INT 14H | ||||
|---|---|---|---|---|---|
| High | Low | High | Low | ||
| AX | 01h | character | AX | Line Status | character |
| BX | BX | ||||
| CX | CX | ||||
| DX | Port Number (0=Com 1, 1=Com2, etc.) | DX | |||
AH=02H—Read Character
| Prior to issuing INT 14H | Upon returning from INT 14H | ||||
|---|---|---|---|---|---|
| High | Low | High | Low | ||
| AX | 02h | AX | Line Status | character | |
| BX | BX | ||||
| CX | CX | ||||
| DX | Port Number (0=Com 1, 1=Com2, etc.) | DX | |||
AH=03H—Status Request
| Prior to issuing INT 14H | Upon returning from INT 14H | ||||
|---|---|---|---|---|---|
| High | Low | High | Low | ||
| AX | 03h | Comm Parm Byte | AX | Line Status | Modem Status |
| BX | BX | ||||
| CX | CX | ||||
| DX | Port Number (0=Com 1, 1=Com2, etc.) | DX | |||