The parallel IEEE-488 interface used on the Commodore PET (1977) computer line was too costly, so a cost reduced version was developed, which consisted of a stripped down, serial version of the IEEE-488 interface, with only a few signals remaining; however, the general protocol layout was kept.

The bus signals are digital single-ended open collector 5 volt TTL and active when low.

If the talker waits more than 200 μs without the Clock line going true (idle state), listeners have to perform End-or-Identify (EOI).

[3] 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".

The host will transmit the specific open command and end it with an EOI signal sequence.

Followed up by ATN line true and "Device number 8, listen", "Secondary address 2, data".

When the host has finished sending data the ATN line is set to true and "Device number 8, unlisten" is sent.

[3] To read a normal file from the floppy device number 8 the command LOAD "filename",8,1 is issued on a Commodore 64.

[10] The VIC-20 computer and the Commodore 1540 and 1541 floppy drives use the MOS Technology 6522 VIA to handle IEC Bus transmissions.