Information Technology Reference
In-Depth Information
IRQ14).
The standard allows for the connection of two disk drives in a daisy-chain configuration.
This can cause problems because both drives have controllers within their drives. The pri-
mary drive (Drive 0) is assigned as the master and the secondary driver (Drive 1) as the
slave. A drive is set as a master or a slave by setting jumpers on the disk drive. They can also
be set by software using the cable select (CSEL) pin on the interface.
EIDE has various modes (ANSI modes) of operation, these are
•
Mode 0 - 600 ns read/write cycle time, 3.3 MB/s burst data transfer rate.
•
Mode 1 - 383 ns read/write cycle time, 5.2 MB/s burst data transfer rate.
•
Mode 2 - 240 ns read/write cycle time, 8.3 MB/s burst data transfer rate.
•
Mode 3 - 180 ns read/write cycle time, 11.1MB/s burst data transfer rate.
•
Mode 4 - 120 ns read/write cycle time, 16.6MB/s burst data transfer rate.
Table 6.3
IDE connections
Pin
IDE signal
AT signal
Pin
IDE signal
AT signal
1
RESET
RESET DRV
2
GND
-
3
D7
SD7
4
D8
SD8
5
D6
SD6
6
D9
SD9
7
D5
SD5
8
D10
SD10
9
D4
SD4
10
D11
SD11
11
D3
SD3
12
D12
SD12
13
D2
SD2
14
D13
SD13
15
D1
SD1
16
D14
SD14
17
D0
SD0
18
D15
SD15
19
GND
-
20
KEY
-
21
DRQ
3
DRQ
3
22
GND
-
23
IOW
IOW
24
GND
-
25
IOR
IOR
26
GND
-
27
IOCHRD
Y
I
OCHRD
Y
28
CSEL
-
29
DACK3
DACK3
30
GND
-
31
IRQ14
IRQ14
32
IOCS16
IOCS16
33
Address bit 1
SA1
34
PDIAG
-
35
Address
bit 0
SA0
36
Address
bit 2
SA2
37
CS1
FX
-
38
CS3FX
-
-
39
SP / DA
-
40
GND
6.8 IDE communication
The IDE (or AT bus) is the de facto standard for most hard disks in PCs. It has the advantage
over older type interfaces that the controller is integrated into the disk drive. Thus the com-
puter only has to pass high-level commands to the unit and the actual control can be achieved
with the integrated controller. Several companies developed a standard command set for an
ATA (AT attachment). Commands include:
•
Read sector buffer - reads contents of the controller's sector buffer.
•
Write sector buffer - writes data to the controller's sector buffer.
