Changes
/* Ports */
* Reading from the write only ports (or unused ports) returns databus values.
* The bits in the interrupt port (#6) are always updated (e.g. when a command is completed bit 2 is set). An interrupt request to the Z80 will only be triggered if the corresponding interrupt request is enabled in register R#9.
* If a command transfers data, and it expects data to be written (e.g. LMMC) to the command data port (P#2), then you can't use a read of the command data port to clear the data request. It must be a write. Similarly, if a command requests data to be read (e.g. LMCM) then you can use a write to the command data port to clear the data request.
