PC87415 datasheet(21/42 Pages) NSC

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70 Functional Description (Continued)

7313 PIO Single Sector Writes

This class includes the following commands

Format

Write buffer

Write Sector(s)

Execution includes the transfer of one or more sectors of

data from the CPU to the drive

a The CPU writes any required parameters to the Features

Sector Count Sector Number Cylinder and DriveHead

registers

b The CPU writes the command code to the Command

c The CPU polls the drive to see if the drive is ready (DRQ

is set in the drive Status Register)

d The CPU writes one sector of data via the Data Register

e When the drive has completed processing the sector it

generates an interrupt request

f After detecting the interrupt the CPU reads the Status

the drive clears the interrupt request

g If transfer of another sector is required the above se-

quence is repeated from c

TLF12497 – 5

7314 PIO Block Mode Writes

This class includes the following command

Write multiple

Execution includes the transfer of a block of sectors of data

from the CPU to the drive

a The CPU writes any required parameters to the Features

Sector Count Sector Number Cylinder and DriveHead

registers

b The CPU writes the command code to the Command

c The CPU polls the drive to see if the drive is ready (DRQ

is set in the drive Status Register)

d The CPU writes one block of sectors of data via the Data

e When the drive has completed processing the block of

sectors it generates an interrupt request

f After detecting the interrupt the CPU reads the Status

the drive clears the interrupt request

g If transfer of another block of sectors is required the

above sequence is repeated from c

TLF12497 – 6

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