== Accessing the FDC 765 ==
The Data Register (Port FB7Fh) is used to write Commands and Parameters, to read/write data bytes, and to receive result bytes. These three operations are called Command-, Execution-, and Result-Phase. The Main Status Register signalizes when the FDC is ready to send/receive the next byte through the Data Register.
aThe Data Register (Port FB7Fh) is used to write Commands and Parameters, to read/write data bytes, and to receive result bytes. These three operations are called Command -, Execution-, and Result-Phase:* Command Phase :A command consists of a command byte (eventually including the MF, MK, SK bits), and up to 8 parameter bytes.
A command consists of a command byte * Execution Phase : During this phase, the actual data is transferred (eventually including if any). Usually that are the MF, MK, SK bitsdata bytes for the read/written sector(s), and up to eight parameter except for the Format Track Command, in that case 4 bytesfor each sector are transferred.
b. Execution * Result Phase: Returns up to 7 result bytes (depending on the command) that are containing status information. The Recalibrate and Seek Track commands do not return result bytes directly, instead the program must wait until the Main Status Register signalizes that the command has been completed, and then it must (!) send a Sense Interrupt State command to 'terminate' the Seek/Recalibrate command.
During this phase, the actual data is transferred (if any). Usually that are the data bytes for the read/written sector(s), except for the Format Track Command, in that case four bytes for each sector are transferred. c. Result Phase Returns up to seven result bytes (depending on the command) that are containing status information. The Recalibrate and Seek Track commands do not return result bytes directly, instead the program must wait until the Main Status Register signalizes that when the command has been completed, and then it must (!) FDC is ready to send a Sense Interrupt State command to 'terminate' /receive the next byte through the Seek/Recalibrate commandData Register.
== FDC Command Table ==
