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FDC37B774 Datasheet(PDF) 57 Page - SMSC Corporation |
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FDC37B774 Datasheet(HTML) 57 Page - SMSC Corporation |
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57 / 196 page  57 Format A Track The Format command allows an entire track to be formatted. After a pulse from the IDX pin is detected, the FDC starts writing data on the disk including gaps, address marks, ID fields, and data fields per the IBM System 34 or 3740 format (MFM or FM respectively). The particular values that will be written to the gap and data field are controlled by the values programmed into N, SC, GPL, and D which are specified by the host during the command phase. The data field of the sector is filled with the data byte specified by D. The ID field for each sector is supplied by the host; that is, four data bytes per sector are needed by the FDC for C, H, R, and N (cylinder, head, sector number and sector size respectively). After formatting each sector, the host must send new values for C, H, R and N to the FDC for the next sector on the track. The R value (sector number) is the only value that must be changed by the host after each sector is formatted. This allows the disk to be formatted with nonsequential sector addresses (interleaving). This incrementing and formatting continues for the whole track until the FDC encounters a pulse on the IDX pin again and it terminates the command. Table 25 contains typical values for gap fields which are dependent upon the size of the sector and the number of sectors on each track. Actual values can vary due to drive electronics. FORMAT FIELDS SYSTEM 34 (DOUBLE DENSITY) FORMAT GAP4a 80x 4E SYNC 12x 00 IAM GAP1 50x 4E SYNC 12x 00 IDAM C Y L H D S E C N O C R C GAP2 22x 4E SYNC 12x 00 DATA AM DATA C R C GAP3 GAP 4b 3x C2 FC 3x A1 FE 3x A1 FB F8 SYSTEM 3740 (SINGLE DENSITY) FORMAT GAP4a 40x FF SYNC 6x 00 IAM GAP1 26x FF SYNC 6x 00 IDAM C Y L H D S E C N O C R C GAP2 11x FF SYNC 6x 00 DATA AM DATA C R C GAP3 GAP 4b FC FE FB or F8 PERPENDICULAR FORMAT GAP4a 80x 4E SYNC 12x 00 IAM GAP1 50x 4E SYNC 12x 00 IDAM C Y L H D S E C N O C R C GAP2 41x 4E SYNC 12x 00 DATA AM DATA C R C GAP3 GAP 4b 3x C2 FC 3x A1 FE 3x A1 FB F8 |
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