Next, issuing commands to the controller

Each command finishes by issuing a MECHA controller interrupt which signals on interrupt line 1 (CARTRIDGE Interrupt) to the main deck CPU. The interrupt is cleared by setting the MECHA interrupt reset bit in the control/status register.

Reading sectors

First set the track with a Read/Seek Command to the desired track. Check that the Index Lock signal in the track register is set when the track is found. Stop the Sequencer (Raw Sector Format). Set the Sector Size and Sectors per Block in the appropriate registers. Restart the Sequencer. Reset the BM(Buffer Manager?) Set the Start Sector index in the control/status register and set the bit to start the BM. Reading sectors only looks at the C1 (Error detection) bytes. It will not use the C2 (Error Correction bytes. Each sector read will set the DREQ (Data Request) flag and signal a BM interrupt when the sector buffer is ready. When 17 sectors have been read without and C1 Errors, the BM is reset to end the transfer.

Reading Blocks/Tracks

Starts like reading a sector. If reading a track the XFER_BLKS flag is set in the control/status register before starting the BM. When the data sectors (set to 85) in the block have been transferred, the BM starts reading the C2 sectors to the C2 buffer. The first three only signal a BM interrupt, with out setting the DREQ flag. The fourth (last) C2 sector sets the C2_XFER flag when it sends an interrupt. After the C2 sectors, there is a gap sector which will not be read to a buffer, but will send a BM interrupt with no flags set. If in block mode, the transfer stops. In in track mode, the transfer continues to the second (last) block of the track.