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PC8477BVF-1 Datasheet(PDF) 26 Page - National Semiconductor (TI) |
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PC8477BVF-1 Datasheet(HTML) 26 Page - National Semiconductor (TI) |
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26 / 54 page  40 Command Set Description (Continued) 4211 Read ID Command The Read ID command finds the next available Address Field and returns the ID bytes (track head sector bytes per sector) to the mP in the Result Phase There is no data transfer during the Execution Phase of this command An interrupt will be generated when the Execution Phase is completed The controller first simulates the Motor On time for the se- lected drive internally The user must turn on the drive motor directly by enabling the appropriate drive and motor select disk interface outputs with the Digital Output Register (DOR) The Read ID command does not perform an implied seek After waiting the Motor On time the controller starts the Data Separator and waits for the Data Separator to find the next sector Address Field If an error condition occurs the IC bits in ST0 are set to Abnormal Termination and the controller enters the Result Phase Possible errors are 1 The mP aborted the command by writing to the FIFO If there is no disk in the drive the controller will hang up The mP must then take the controller out of this hung state by writing a byte to the FIFO This will put the con- troller into the Result Phase 2 Two index pulses were detected since the search began and no AM has been found If the Address Field AM was never found the MA bit is set in ST1 4212 Read A Track Command The Read a Track command reads sectors in physical order from the selected drive and makes the data available to the host This command is similar to the Read Data command except for the following differences 1 The controller waits for the index pulse before searching for a sector Address Field If the mP writes to the FIFO before the index pulse the command will enter the Result Phase with the IC bits in ST0 set to Abnormal Termina- tion 2 A comparison of the sector Address Field ID bytes will be performed except for the sector number The internal sector address is set to 1 and then incremented for each successive sector read 3 If the Address Field ID comparison fails the controller sets ND in ST1 but continues to read the sector If there is a CRC error in the Address Field the controller sets CE in ST1 but continues to read the sector 4 Multi-track and Skip operations are not allowed SK and MT should be set to 0 5 If there is a CRC error in the Data Field the controller sets CE in ST1 and CD in ST2 but continues reading sectors 6 The controller reads a maximum of EOT physical sectors There is no support for multi-track reads 4213 Recalibrate Command The Recalibrate command is very similar to the Seek com- mand The controller sets the Present Track Register (PTR) of the selected drive to zero It then steps the head of the selected drive out until the TRK0 disk interface input signal goes active or until the maximum number of step pulses have been issued See Table 4-9 for the maximum recali- brate step pulse values based on the R255 and ETR bits in the Mode command If the number of tracks on the disk drive exceeds the maximum number of recalibrate step pulses another Recalibrate command may need to be is- sued TABLE 4-9 Maximum Recalibrate Step Pulses Based on R255 and ETR R255 ETR Maximum Recalibrate Step Pulses 0 0 85 (default) 1 0 255 0 1 3925 1 1 4095 After the last command byte is issued the DRx BUSY bit is set in the MSR for the selected drive The controller will simulate the Motor On time and then enter the Idle Phase The execution of the actual step pulses occurs while the controller is in the Drive Polling Phase An interrupt will be generated after the TRK0 signal is asserted or after the maximum number of recalibrate step pulses are issued There is no Result Phase Recalibrates on more than one drive at a time should not be issued for the same reason as explained in the Seek command No other command except the Sense Interrupt command should be issued while a Re- calibrate command is in progress 4214 Relative Seek Command The Relative Seek command steps the selected drive in or out a given number of steps This command will step the readwrite head an incremental number of tracks as op- posed to comparing against the internal present track regis- ter for that drive The Relative Seek parameters are defined as follows DIR ReadWrite Head Step Direction Control 0 e Step Head Out 1 e Step Head In RTN Relative Track Number This value will determine how many incremental tracks to step the head in or out from the current track number The controller will issue RTN number of step pulses and update the Present Track Register for the selected drive The one exception to this is if the TRK0 disk input goes active which indicates that the drive readwrite head is at the outermost track In this case the step pulses for the Relative Seek are terminated and the PTR value is set ac- cording to the actual number of step pulses issued The arithmetic is done modulo 255 The DRx BUSY bit in the MSR is set for the selected drive The controller will simu- late the Motor On time before issuing the step pulses After the Motor On time the controller will enter the Idle Phase The execution of the actual step pulses occurs in the Idle Phase of the controller After the step operation is complete the controller will gen- erate an interrupt There is no Result Phase Relative Seeks on more than one drive at a time should not be issued for the same reason as explained in the Seek command No other command except the Sense Interrupt command should be issued while a Relative Seek command is in prog- ress 26 |
Similar Part No. - PC8477BVF-1 |
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Similar Description - PC8477BVF-1 |
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