Copyright(C) 1994 Terumasa KODAKA , Takeshi KONO


■CMT (cassette tape) BIOS
Overview of CMT BIOS
               o The CMT BIOS exists in the main BIOS ROM. Only the PC-9801 original, E, F, M, U, VM2, VF, UV2, VX2, VX21, VM21, UV21, and UX are supported.
                 To use the CMT BIOS, the PC-9801-13 (CMT interface board) is required.
                 It also exists in the PC-98LT and HA, but it is meaningless because the CMT interface board cannot be connected.
               o On models that do not support the CMT interface, executing INT 1Ah - Function 00-03h, 06-0Fh will end with AH=00h.
                 Executing INT 1Ah - Function 04h, 05h will end with AH=02h.


INT 1Ah - Function 00h
Category         CMT BIOS
Name             No function
Target           Normal
Input            AH=00h
Output           AH=00h
Explanation    o
Related


INT 1Ah - Function 01h
Category         CMT BIOS
Name             Cassette motor OFF
Target           Normal
Input            AH=01h
Output           AH=00h (normal end)
Explanation    o Sets the CMT I/F relay to the motor OFF state.
                 At the same time, sets it to 1200 baud.
Related          I/O 0091h

INT 1Ah - Function 02h
Classification   CMT BIOS
Name             Cassette motor ON (data read mode)
Target           Normal
Input            AH=02h
                 AL=baud rate
                   00h: 600baud
                   80h: 1200baud
Output           AH=00h (normal end)
Explanation    o Turns the CMT I/F relay to the motor ON state, enabling data reading.
Related


INT 1Ah - Function 03h
Category         CMT BIOS
Name             Cassette motor ON (data write mode)
Target           Normal
Input            AH=03h
                 AL=Baud rate
                   00h: 600baud
                   80h: 1200baud
Output           AH=00h (normal end)
Explanation    o Turns the CMT I/F relay to the motor ON state, enabling data writing.
Related


INT 1Ah - Function 04h
Category         CMT BIOS
Name             Data write
Target           Normal
Input            AH=04h
                 AL=Write data
Output           AH=00h (normal end)
                    02h (timeout)
Explanation    o Writes a 1-byte value to the CMT. INT 1Ah - Function 03h must be executed before executing this function.
Related          INT 1Ah - Function 03h


INT 1Ah - Function 05h
Classification   CMT BIOS
Name             Data Read
Target           Normal
Input            AH=05h
                 AL=Error notification
                   01h: No notification
                   00h: Notification
Output           AH=00h (normal end)
                    02h (timeout)
                    27h (read error: framing error, overrun error occurred)
Explanation    o Reads 1 byte value from CMT. INT 1Ah - Function 02h must be executed before executing this function.
Related          INT 1Ah - Function 02h