Shugart Associates
Although Shugart Associates did not market items directly for Heathkit computers, Heath Company used the SASI interface for it's Z-67 Winchester Disk Drive System.
Shugart Associates created both the 5 1/4" Floppy drive and the SASI and SCSI standards.
Here are the specifications for SASI (Shugart Associates System Interface).
Rev A - sasi_r0a.pdf
Rev C (1/29/82) - sasi_r0c.pdf
For more information about Shugart Associates, see the Shugart Associates page on wikipedia.
