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PC8477BV-1 Datasheet(PDF) 19 Page - National Semiconductor (TI) |
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PC8477BV-1 Datasheet(HTML) 19 Page - National Semiconductor (TI) |
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19 / 54 page  40 Command Set Description (Continued) 42 COMMAND DESCRIPTION 421 Configure Command The Configure Command will control some operation modes of the controller It should be issued during the initialization of the PC8477B after power up The function of the bits in the Configure registers is described below These bits are set to their default values after a hardware reset The value of each bit after a software reset is explained The default value of each bit is denoted by a ‘‘bullet’’ to the left of each item EIS Enable Implied Seeks Default after a software reset 0 e Implied seeks disabled through Configure command Implied seeks can still be enabled through the Mode command when EIS e 0 (default) 1 e Implied seeks enabled for a read write scan or veri- fy operation A seek and sense interrupt operation will be performed prior to the execution of the read write scan or verify operation The IPS bit does not need to be set FIFO Enable FIFO for Execution Phase data transfers De- fault after a software reset if the LOCK bit is 0 If the LOCK bit is 1 then the FIFO bit will retain its previous value after a software reset 0 e FIFO enabled for both reads and writes 1 e FIFO disabled (default) POLL Disable for Drive Polling Mode Default after a soft- ware reset 0 e Enable polling mode An interrupt is generated after a reset (default) 1 e Disable drive polling mode If the Configure com- mand is issued within 500 ms of a hardware or soft- ware reset then an interrupt will not be generated In addition the four Sense Interrupt commands to clear the ‘‘Ready Changed State’’ of the four logical drives will not be required THRESH The FIFO threshold in the Execution Phase of read and write data transfers Programmable from 00 to 0F hex Defaults to 00 after a software reset if the LOCK bit is 0 If the LOCK bit is 1 then THRESH will retain its value A high value of THRESH is suited for slow response systems and a low value of THRESH is better for fast response sys- tems PRETRK Starting track number for write precompensation Programmable from track 0 (‘‘00’’) to track 255 (‘‘FF’’) De- faults to track 0 (‘‘00’’) after a software reset if the LOCK bit is 0 If the LOCK bit is 1 then PRETRK will retain its value 422 Dumpreg Command The Dumpreg command is designed to support system run- time diagnostics and application software development and debug This command has a one byte command phase and a ten byte result phase which return the values of parame- ters set in other commands That is the PTR (Present Track Register) contains the least significant byte of the track the microcode has stored for each drive The Step Rate Time Motor Off and Motor On Times and the DMA bit are all set in the Specify command The sixth byte of the result phase varies depending on which commands have been previously executed If a for- mat command has previously been issued and no reads or writes have been issued since then then this byte will con- tain the Sectors per track value If a read or a write com- mand has been executed more recently than a format com- mand this byte will contain the End of Track value The LOCK bit is set in the Lock command The eighth result byte also contains the bits programmed in the Perpendicular Mode command The last two bytes of the Dumpreg Result Phase are set in the Configure command After a hardware or software reset the parameters in the result bytes will be set to their appropriate default values Note Some of these parameters are unaffected by a software reset de- pending on the state of the LOCK bit 423 Format Track Command This command will format one track on the disk in IBM ISO or Perpendicular Format After the index hole is detected data patterns are written on the disk including all Gaps Ad- dress Marks Address Fields and Data Fields The exact format is determined by the following parameters 1 The MFM bit in the Opcode (first command) byte which determines the format of the Address Marks and the en- coding scheme 2 The IAF bit in the Mode command which selects be- tween IBM and ISO format 3 The WGATE and GAP bits in the Perpendicular Mode command which select between the conventional and Toshiba Perpendicular format 4 The Bytes per Sector code which determines the sector size 5 The Sectors per Track parameter which determines how many sectors will be formatted on the track 6 The Data Pattern byte which is used as the filler byte in the Data Field of each sector 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 19 |
Similar Part No. - PC8477BV-1 |
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Similar Description - PC8477BV-1 |
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