8088 Microprocessor Hardware

Microprocessor System Modules CPU Memory (RAM, ROM) Peripherals (IO) Data Bus Control Bus Address Bus Keyboard Monitor Printer Mouse Microphone Disk LED LCD SWICH

Memory Von Neumann Architecture Microprocessor Address Lines Data Lines Control Lines

The 8088 Features Has 20 address lines so could address up to 1 Mb of memory ( ) at a time when 8085 could only address 64 kb. The 8088 CPU was the first chip used in IBM’s microcomputers

8088 pin Configuration ( minimum mode )

Power and Ground Pins Vcc – pin 40 Gnd – pin 1 and 20

Address Pins AD0..AD7 A8..A15 A19/S6, A18/S5, A17/S4, A16/S3

Data Pins AD0..AD7

Control Pins MN/MX’ (input) – Indicates what mode the processor is to operate in READY (input) – When given an input LOW, it will go into a wait state CLK (input) – Provides basic timing for the processor – needed by the microprocessor to synchronize signals – ideally a square wave having a constant frequency RESET (input) – Causes the processor to immediately terminate its present activity – To reset the microprocessor, this must be HIGH for at least 4 clock cycles

Control Pins (Continue) HOLD (input) – Connect this to LOW HLDA (Hold Acknowledge) Active-high output signal. After input on HOLD, the CPU responds with HLDA to signal that the DMA controller can use the buses.

INTR (input) – Interrupt request INTA’ (output) – Interrupt Acknowledge NMI (input) – Non-maskable interrupt Control Pins (Continue)

DEN’ (output) – Data Enable – It is LOW when processor wants to receive data or processor is giving out data DT/R’ (output) – Data Transmit/Receive – When HIGH, direction of data lines is from microprocessor to memory/devices – When LOW, direction of data lines is from memory/devices to microprocessor IO/M’ (output) – Device/Memory – When HIGH, microprocessor wants to access I/O Device – When LOW, microprocessor wants to access memory Control Pins (Continue)

RD’ (output) – When LOW, it indicates that the microprocessor is performing a read access WR’ (output) – When LOW, it indicates that the microprocessor is performing a write access ALE (output) – Address Latch Enable – Provided by the microprocessor to latch address – When this is HIGH, microprocessor is using AD0..AD7, A19/S6, A18/S5, A17/S4, A16/S3 as address lines Control Pins (Continue)

Physical Address=CS*16+IP=FFFF* =FFFF0+0000=FFFF0 At what address does the 8088 wake up

طراحی گذرگاه کنترل در مد مینیمم 8088

IORD IOWR MEMRD MEMWR طراحی گذرگاه کنترل در مد مینیمم 8088

نحوه جداسازی باس آدرس از باس داده بدلیل محدودیت در تعداد پینها، باس های داده و آدرس مالتی پلکس شده اند. برای جداسازی باسها از یک لچ 8 بیتی و سیگنال ALE استفاده میکنیم. سیگنال ALE(Address Latch Enable): سیگنال خروجی Active – High نشان میدهد یک آدرس معتبر بر روی باس آدرس قرار داده شده است.

Processor Timing Diagram of 8088 (Minimum Mode) for Memory or I/O Read ALE T1 CLOCK T2T3T4 AD7 - AD0 A15 - A8 A19/S6 - A16/S3 DT/R __ IO/M __ ____ RD DEN ______ A15 - A8 A7 - A0D7 - D0 (from memory) A19 - A16S6 - S3 if I/O ACCESS this is HIGH, if MEMORY ACCESS this is LOW

74373 D type Latch

Minimum Mode MEMORY D7 - D0Q7 - Q0 OE LE 74LS373 D7 - D4Q7 - Q4 OE LE D3 - D0Q3 - Q0 74LS373 GND D7 - D0 A7 - A0 A15 - A8 A19 - A16 RD WR 8088 AD7 - AD0 A15 - A8 A19/S6 - A16/S3 DEN DT / R IO / M RD WR ALE نحوه جداسازی باس آدرس از باس داده

بافر کردن باس داده برای این منظور از بافر دو جهته (Transciever) استفاده میکنیم. Transciever: Transmitter/Reciever

Minimum Mode

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