Divided by 12 for Controlling Data Wrap
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Conventional flexible diskette controllers, such as the NEC type 765, ccept standard "FM" data during a data window that is low during the lock time of the bit cell and high during the data time. The diagnostic wrap function takes parallel data from the main processor and converts it to FM format serial clock and data bits. Referring to Fig. 1, a diagnostic wrap function circuit is shown which uses a divided by 12 counter to serialize the data and provide the data window. The data wrap occurs when the attachment is placed into a diagnostic mode by setting the diagnostic mode line at the output of data register 10. Then parallel data is provided at the output of data register 10 as 2 clock bits and 2 data bits representing 2 bit cells. This is done every 7 microseconds.