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isa總線標準定義

作者:佚名   來源:不詳   點擊數:x  更新時間:2008年01月08日   【字體:

isa總線標準
ISA 是 Industry Standard Architecture 的縮寫 ISA插槽是基于ISA總線(Industrial Standard Architecture,工業標準結構總線)的擴展插槽,其顏色一般為黑色,比PCI接口插槽要長些,位于主板的最下端。其工作頻率為8MHz左右,為16位插槽,最大傳輸率16MB/sec,可插接顯卡,聲卡,網卡已及所謂的多功能接口卡等擴展插卡。其缺點是CPU資源占用太高,數據傳輸帶寬太小,是已經被淘汰的插槽接口。

 ISA 是8/16bit 的系統總線,最大傳輸速率僅為8MB/s ,但允許多個CPU 共享系統資源。由于兼容性好,它在上個世紀80年代是最廣泛采用的系統總線,不過它的弱點也是顯而易見的,比如傳輸速率過低、CPU占用率高、占用硬件中斷資源等。后來在PC‘98 規范中,就開始放棄了ISA 總線,而Intel 從i810 芯片組開始,也不再提供對ISA 接口的支持。

    ISA總線擴展插槽由兩部分組成,一部分有62引腳,其信號分布及名稱與PC/XT總線的擴展槽基本相同,僅有很小的差異。另一部分是AT機的添加部分,由36引腳組成。這36引腳分成兩列,分別稱為C列和D列。  

isa接口卡的外觀

 

isa插槽的外觀

 

ISA接口引腳定義


引腳

定義

方向

說明

A1

/I/O CH CK

I/O channel check; active low=parity error

A2

D7

Data bit 7

A3

D6

Data bit 6

A4

D5

Data bit 5

A5

D4

Data bit 4

A6

D3

Data bit 3

A7

D2

Data bit 2

A8

D1

Data bit 1

A9

D0

Data bit 0

A10

I/O CH RDY

I/O Channel ready, pulled low to lengthen memory cycles

A11

AEN

Address enable; active high when DMA controls bus

A12

A19

Address bit 19

A13

A18

Address bit 18

A14

A17

Address bit 17

A15

A16

Address bit 16

A16

A15

Address bit 15

A17

A14

Address bit 14

A18

A13

Address bit 13

A19

A12

Address bit 12

A20

A11

Address bit 11

A21

A10

Address bit 10

A22

A9

Address bit 9

A23

A8

Address bit 8

A24

A7

Address bit 7

A25

A6

Address bit 6

A26

A5

Address bit 5

A27

A4

Address bit 4

A28

A3

Address bit 3

A29

A2

Address bit 2

A30

A1

Address bit 1

A31

A0

Address bit 0

B1

GND

 

Ground

B2

RESET

Active high to reset or initialize system logic

B3

+5V

 

+5 VDC

B4

IRQ2

Interrupt Request 2

B5

-5VDC

 

-5 VDC

B6

DRQ2

DMA Request 2

B7

-12VDC

 

-12 VDC

B8

/NOWS

No WaitState

B9

+12VDC

 

+12 VDC

B10

GND

 

Ground

B11

/SMEMW

System Memory Write

B12

/SMEMR

System Memory Read

B13

/IOW

I/O Write

B14

/IOR

I/O Read

B15

/DACK3

DMA Acknowledge 3

B16

DRQ3

DMA Request 3

B17

/DACK1

DMA Acknowledge 1

B18

DRQ1

DMA Request 1

B19

/REFRESH

Refresh

B20

CLOCK

System Clock (67 ns, 8-8.33 MHz, 50% duty cycle)

B21

IRQ7

Interrupt Request 7

B22

IRQ6

Interrupt Request 6

B23

IRQ5

Interrupt Request 5

B24

IRQ4

Interrupt Request 4

B25

IRQ3

Interrupt Request 3

B26

/DACK2

DMA Acknowledge 2

B27

T/C

Terminal count; pulses high when DMA term. count reached

B28

ALE

Address Latch Enable

B29

+5V

 

+5 VDC

B30

OSC

High-speed Clock (70 ns, 14.31818 MHz, 50% duty cycle)

B31

GND

 

Ground

 

 

 

 

C1

SBHE

System bus high enable (data available on SD8-15)

C2

LA23

Address bit 23

C3

LA22

Address bit 22

C4

LA21

Address bit 21

C5

LA20

Address bit 20

C6

LA18

Address bit 19

C7

LA17

Address bit 18

C8

LA16

Address bit 17

C9

/MEMR

Memory Read (Active on all memory read cycles)

C10

/MEMW

Memory Write (Active on all memory write cycles)

C11

SD08

Data bit 8

C12

SD09

Data bit 9

C13

SD10

Data bit 10

C14

SD11

Data bit 11

C15

SD12

Data bit 12

C16

SD13

Data bit 13

C17

SD14

Data bit 14

C18

SD15

Data bit 15

D1

/MEMCS16

Memory 16-bit chip select (1 wait, 16-bit memory cycle)

D2

/IOCS16

I/O 16-bit chip select (1 wait, 16-bit I/O cycle)

D3

IRQ10

Interrupt Request 10

D4

IRQ11

Interrupt Request 11

D5

IRQ12

Interrupt Request 12

D6

IRQ15

Interrupt Request 15

D7

IRQ14

Interrupt Request 14

D8

/DACK0

DMA Acknowledge 0

D9

DRQ0

DMA Request 0

D10

/DACK5

DMA Acknowledge 5

D11

DRQ5

DMA Request 5

D12

/DACK6

DMA Acknowledge 6

D13

DRQ6

DMA Request 6

D14

/DACK7

DMA Acknowledge 7

D15

DRQ7

DMA Request 7

D16

+5 V

 

 

D17

/MASTER

Used with DRQ to gain control of system

D18

GND

 

Ground

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