Copyright (C) 1994,1995,1996,1997 Terumasa KODAKA, Takeshi KONO


■ CMT interface board

Target        PC-9801-03･13
Explanation o PC-9801-03･13 is for connecting an audio cassette tape recorder.
              It is an interface board.
Related       INT 1Ah --Function 00 ~ 05h
              0000:05C2 ~ 05C5h


I/O           0091h, 0093h
Name          8251A control
Target        PC-9801-03･13
Chip          8251A equivalent
function
              -----------+-------+-----+-----------------------------------------------------------
              I/O address| Width | R/W | Contents
              -----------+-------+-----+-----------------------------------------------------------
              0091h      | BYTE  | R/W | Data Read / Data Write
              0093h      | BYTE  | R   | Status Lead
              0093h      | BYTE  | W   | Mode / Command Light
              -----------+-------+-----+-----------------------------------------------------------
Explanation o 8251A register. See the 8251A data sheet for details.
            u In high resolution mode, another function is assigned to I / O 0091h and 0093h.
Related       I/O 0095h, 0097h


I/O           0095h, 0097h
Name          control port
Target        PC-9801-03･13
function
              [READ] None
              [WRITE]
              bit 7: BS baud rate switching
                      1 = 1200bps
                      0 = 600bps
              bit 6: CINH write data prohibited
                      1 = ON
                      0 = OFF
              bit 5: CONT motor ON / OFF
                      1 = ON
                      0 = OFF
              bit 4: CLK switching of SCLK 8251A
                      1 = 8MHz
                      0 = 5MHz
              bit 3: unused
              bit 2: TxEMP interrupt enable control
              bit 1: RxRDY interrupt enable control
              bit 0: TxRDY interrupt enable control
                      1 = Interrupt enabled
                      0 = Interrupt disabled
Explanation o CMT interface control port.
            o I/O addresses 0095h and 0097h are the same.
Related       I/O 0091h, 0093h