by pulling the Data line true within 1000 µs. After this the talker sets the Clock line true and listener sets the Data line true thus back where the transmission begun. If an EOI is signaled by holding the Clock line false the transmission is ended and the listener acknowledge this by pulling the Data line true for 200 µs. The ATN line is set to true and bytes are sent like above to all devices, but the byte is interpreted as one of the commands "Talk," "Listen," "Untalk," and "Unlisten". That tell a specific device to become a talker or listener. Only devices with matching device numbers switch into talk and listen mode. A secondary address may also follow. On higher logical level the host will set the ATN line to true and transmit the bytes "Device number 8, listen", "Secondary address 2, open". Next it will set the ATN line false and the host then becomes the talker, holding the Clock line true. The device will be the listener, holding the Data line true. The host will transmit the specific open command and end it with an EOI signal sequence. After this the host will set with ATN line true, "Device number 8, unlisten". Followed up by ATN line true and "Device number 8, listen", "Secondary address 2, data". Then the host sets the ATN line false and sends the data. When the host has finished sending data the ATN line is set to true and "Device number 8, unlisten" is sent. When it is necessary to switch roles and make the host a listener and the device a talker the occurs after a talk command has been sent to the device. The host sets the Data line true and releases the Clock line to false. The device waits for the Clock line to go false and then pulls it to true and release the Data line to false. After this sequence the standard talk-listener interaction may follow. To read a normal file from the floppy device number 8 the command LOAD "filename",8,1 is issued on a Commodore 64. That causes the following high level communication to take place: The Commodore 1541 floppy drive uses a slower Commodore 64 compatible mode which can be deactivated for faster speed by using the command OPEN 15,8,15,"UI-":CLOSE 15. Device numbering Device number 0–3 are not associated with the Commodore bus. Host