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。
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isa接口卡的外觀 |
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isa插槽的外觀 |
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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 |
