PC87415VCG datasheet(20/42 Pages) NSC

20 / 42 page

70 Functional Description (Continued)

TABLE I ATA Port Definition

Address

Read Function

Write Function

COMMAND BLOCK REGISTERS

1F0

Data (16 bits)

1F1

Error Register

Features

1F2

Sector Count

1F3

Sector Number

1F4

Cylinder Low

1F5

Cylinder High

1F6

DriveHead

1F7

Status

Command

CONTROL BLOCK REGISTERS

3F6

Alternate Status

Device Control

3F7

Drive Address

Not Used

(and floppy DSKCHG)

731 IDE Protocol

This section is provided as a reference only The device

passes these commands to the drive

Commands that transfer data can be grouped into different

classes according to the protocol followed for command ex-

ecution The different classes are

PIO Single sector read

PIO Block Mode read

PIO Single sector write

PIO Block Mode write

DMA Mode

7311 PIO Single Sector Reads

This class includes the following commands

Identify drive

Read buffer

Read sector(s)

Execution includes the transfer of one or more sectors of

data from the drive to the CPU

a The CPU writes any requIred parameters to the Fea-

tures Sector Count Sector Number Cylinder and Drive

Head registers

b The CPU writes the command code to the Command

c When a sector of data is available the drive issues an

interrupt to the CPU

d After detecting the interrupt the CPU reads the Status

ister In response to the Status Register being read the

drive clears the interrupt request

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

quence is repeated from c

TLF12497 – 3

The above sequence is repeated if accesses are directed to another channel

7312 PIO Block Mode Reads

This class includes the following command

Read multiple

Execution includes the transfer of a block of sectors of data

from the drive to the CPU

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 When the block of sectors of data is available the drive

issues an interrupt to the CPU

d After detecting the interrupt the CPU reads the Status

the drive clears the interrupt request

TLF12497 – 4

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