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INT 14h, 05h (05) Control Extended Communications Port PS/2
Sets or Reads the Modem Control Register.
AL = 0 Read Modem Control Register
On entry: AH 05h
AL 0
DX RS-232C communications line to use
(0, 1, 2, 3)
Returns: BL = Modem Control Register
Bit 4 = 1 . Loop
Bit 3 = 1 . Out2
Bit 2 = 1 . Out1
Bit 1 = 1 . Request to send
Bit 0 = 1 . Data terminal ready
AL = Modem Status (See Service 03h)
AH = Line Status (See Service 03h)
---------------------------------------------------------------------------
AL = 1 Write to Modem Control Register
On entry: AH 05h
AL 1
DX RS-232C communications line to use
(0, 1, 3)
BL = Modem Control Register
Bit 4 = 1 . Loop
Bit 3 = 1 . Out2
Bit 2 = 1 . Out1
Bit 1 = 1 . Request to send
Bit 0 = 1 . Data terminal ready
Returns: AL = Modem Status (See Service 03h)
AH = Line Status (See Service 03h)
---------------------------------------------------------------------------
With this service, you can read from or write to the modem control
register. This gives you advanced control over the modem; you can
configure it a number of ways as shown above. You can also set it to loop
for diagnostic purposes.
There are two subservices; Subservice 0 is for reading the modem
state (returned in BL), and Subservice 1 is for writing to it (set BL
appropriately). See Service 03h for more information on the modem state.
See Also:
INT 14h, 03h
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