AH = 01h: Transmit One Character
This function transmits one character through the serial port. The sequence of operations performed is
- 03h is written to the Modem Control Register (RTS and DTR).
- Loop waiting for xx11xxxxb (DSR and CTS) in the Modem Status Register.
- Loop waiting for xx1xxxxxb (Xmit Buff Reg Empty) in the Line Status Register.
- Reset display timeout counter (Avoid Auto-Turn Off).
- Output char to the Xmit Buffer.
Either of the above loops can result in a timeout error.
- Input: AH = 01h
AL = Character to transmit
DX = Port# (0 = Built-In Serial Port)
- Output: AH = LSR (except: Only bits 1,2,3,4, and 7 are returned.)
- Error conditions: Possible timeout (AH[7])
- Registers modified: AH