PC87311AVF datasheet(30/78 Pages) NSC

30 / 78 page

40 FDC Command Set Description (Continued)

To allow for flexible formatting the mP must supply the four

Address Field bytes (track head sector bytes per sector

code) for each sector formatted during the Execution

Phase This allows for non-sequential sector interleaving

This transfer of bytes from the mP to the controller can be

done in the DMA or Non-DMA mode with the FIFO enabled

or disabled

The Format command terminates when the index hole is

detected a second time at which point an interrupt is gener-

ated Only the first three status bytes in the Result Phase

are significant The Format Gap byte in the Command

Phase is dependent on the data rate and type of disk drive

and will control the length of GAP3 Some typical values for

the programmable GAP3 are given in Table 4-1 (next page)

Figure 4-1 shows the track format for the three types of

formats supported by the floppy controller

TLF11362 – 5

Notes

FE e Data Pattern of FE Clock Pattern of C7

FC e Data Pattern of FC Clock Pattern of D7

FB e Data Pattern of FB Clock Pattern of C7

F8 e Data Pattern of F8 Clock Pattern of C7

A1 e Data Pattern of A1 Clock Pattern of 0A

C2 e Data Pattern of C2 Clock Pattern of 14

All byte counts in decimal

All byte values in hex

CRC uses standard polynomial x16 a x12 a x5 a 1

Perpendicular Format GAP2 e 41 bytes for 1 Mbs

All other data rates use GAP2 e 22 bytes

FM mode is not guaranteed through functional testing

FIGURE 4-1 IBM Perpendicular and ISO Formats Supported by Format Command

PC87311AVF Datasheet(PDF) 30 Page - National Semiconductor (TI)