chpt2 how software and hardware work together
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8/9/2019 Chpt2 How Software and Hardware Work Together
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Lesson 2Lesson 2
How Software and Hardware Work Together
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Slide 2Ver 1.0 10 April 2001
ObjectivesObjectives
Understand how the devices communicates
Introduction to system resources
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Slide 4Ver 1.0 10 April 2001
Interrupt RequestInterrupt Request
Device interruptCPU when it need CPU services usingINT wire
Eg When keyboard is pressed, INT wire is charged. The CPUstops what it is doing and run a BIOS routine (program) toquery the keyboard
To regulates data traffic on the I/O busThe adapter or unit on the I/O bus uses the interrupt to signalrequest to the CPU that it wants to send or receive data
Most IRQ wires are assigned to certain devices
16 IRQsOnly 15 IRQ can be used
IRQ 2 is wired to IRQ 9 (they are the same)
2 IRQ controllers, joined by IRQ 2 and IRQ 9
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Slide 5Ver 1.0 10 April 2001
IRQ ControllersIRQ Controllers
IRQ 8
IRQ 9 (dont exist)IRQ 10IRQ 11IRQ 12IRQ 13
IRQ 14
IRQ 15
IRQ 0IRQ 1
IRQ 2/9IRQ 3IRQ 4IRQ 5
IRQ 6
IRQ 7
IRQ2 join to IRQ9
Int
Intel CPU
IRQ Controller IRQ Controller
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Slide 6Ver 1.0 10 April 2001
Interrupt RequestInterrupt Request
Physically implemented as wiresIRQ 0, 1 and 8 are hard wired
IRQ is assigned to a device when the PC starts
Sharing of IRQ
PCI devices are able to shareConflict of IRQ
2 or more devices using the same IRQ
Devices with resources conflict will not work
Adjust resources to enable each device to have their
own resources
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Slide 7Ver 1.0 10 April 2001
IRQ TableIRQ Table
IRQ Devices
0 System timer
1 Keyboard controller
2 Open for use
3 COM 2, COM 4
4 COM 1, COM 3
5 LPT2 (printer)
6 Floppy drive controller
7 LPT1 (printer)
8 Real-time clock
9 Wired to IRQ 2
10 Open for use
11 Open for use
12 Open for use
13 Math coprocessor
14 Primary hard drive controller
15 Secondary hard drive controller
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Slide 8Ver 1.0 10 April 2001
I/O AddressI/O Address
CPU talks to devices using their I/O addressPhysically, it use a wire call IO/MEM
When voltage is placed on the wire, all devices listen. Thedevice will response if the I/O address matches
All devices have more than 1 I/O addressEg hard disk has preset I/O address 01F0-01FF
Sound card configures its own
2 devices cannot have the same I/O address
Once a device has an I/O address, no other device can
use itTwo ways communication: CPU and a device
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Slide 9Ver 1.0 10 April 2001
Physical wiring & HEXPhysical wiring & HEX
I/O address using 16 wiresDivided into 4 group of 4 wires (4groups x 4 wires)
Using 4 wires to representHexadecimal numbers (seetable)
Eg 01F0 is represented physicallyas:
0000 0001 1111 0000
Binary number Hex0000 All wire off 0
0001 Only 4th wire off 1
0010 Only 3rd wire off 2
0011 3th and 4th on 3
0100 Only 2nd wire on 4
0101 2nd and 4th wire on 5
0110 2nd and 3rd wire on 6
0111 Only 1stwire off 7
1000 Only 1stwire on 8
1001 1stand 4th wire on 9
1010 1st
and 3rd
wire on A1011 2nd wire off B
1100 1stand 2nd wire on C
1101 3rd wire off D
1110 4th wire off E
1111 All wires on F
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Slide 10Ver 1.0 10 April 2001
I/O Address TableI/O Address Table
IRQ I/O Address Device
0 040-05F System timer
1 060-06F Keyboard controller
2 0A0-0AF Access to IRQs above 7
4 3F8-3FFCOM1
3 2F8-2FF COM2
4 3E8-3EF COM3
3 2E8-2EF COM4
6 03F-3F7 Floppy
7 378-37F Parallel Port (LPT1)
14 1F0-1F7 Primary IDE
15 170-177 Secondary IDE
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Slide 11Ver 1.0 10 April 2001
Direct Memory AccessDirect Memory Access
Enables system to run background applicationwithout interfering the CPU
Creating background sounds in games
Access floppy disk drive
To increase system performanceFreed the CPU from handling data transfer tasks
PC has 2 DMA controllers, giving 8 channels0 to 7
Channel 0, 2, and 4 cannot be usedChannel 2 is used by Floppy disk drive
Device activate its assigned DMA channel if it wants to performa DMA data transfer
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Slide 12Ver 1.0 10 April 2001
Direct Memory AccessDirect Memory Access
Use by ISA devicesDMA is Slow
Not suitable for newer devices eg hard disk
Used by slow devices eg floppy drive, tape drive, sound card
Bus Master devicesSkip DMA totally
Popular in Hard disk, known as Ultra DMA
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Slide 13Ver 1.0 10 April 2001
Enabling DMA in Hard Disk (older HDD)Enabling DMA in Hard Disk (older HDD)
Steps:Control Panel
Double-Click System applet
Click Device Manager
Double-click on Disk Drive
Click on selected hard disk
Click on Properties
Click on the Setting tab
Check the DMA box
Note: If problem is encounteredafter enabling DMA, remove thesetting in SAFE MODE
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Slide 14Ver 1.0 10 April 2001
DMA ChannelsDMA Channels
DMA Channels Function Other Users
0 Memory Refresh None
1 Open for Use SCSI, ECP port
2 Floppy drive controller Tape
3 Open for Use ECP port SCSI card,Network Card
4 Not Available Cascade to 0-3
5 Sound Card SCSI
6 Open for Use Sound Card, NIC
7 Open for Use Sound Card, NIC
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Slide 15Ver 1.0 10 April 2001
Device Manager to Find Resources AllocationDevice Manager to Find Resources Allocation
The steps are:Control Panel
System Applet
Device Manager tab
Double-click on Computer
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