introduction:

The 8086 was introduced in 1978, was the first 16-bit microprocessor introduced by Intel Corporation. 8086 and 8088 are internally 16-bit MPU. However 8086 have 16-bit data bus and 8088 have 8-bit data bus. 8086 and 8088 have the ability to address up to 1Mb of memory and 64k of input/output port. Both are manufactured using High performance Metal Oxide Semiconductor (HMOS) technology. The 8086 and 8088 are housed in a 40-pin dual in-lined jacket and many pins have multiple functions.

bus structure of 8088/8086:

8088 vs 8086 interface signals-pins:

                                                                               8088                                                               8086

                 

pins and there functions:

PIN-19: Both MPU’s have same function CLK (The system clock function). The clock speed supported by 8086 family are

(standard 8086 operate at 5MHz clock speed whereas 8086-2 and 8086-1 operate at 8Mhz and 10MHz. Standard 8088 operates at 5MHz whereas 8088-2 operates at 8MHz clock speed)

In this fig. our concern is with its outputs we have OSC (oscillator frequency) one third of OSC is CLK (clock frequency) and one half of CLK is PCLK (peripheral frequency) Pin-8 act as input for MPU Pin-19.

PIN-(2-16 & 35-39): 8088/8086 IC generate address signals (A19-A0). This is 20-bit address bus allows the processor to access 1Mb, memory storage locations.

In 8086 Pin 2 to 16 and Pin 39 generates/receives 16-bit data signals (D15-D0) to read/write data into the CPU registers. Thus Data bus supports bi-directional data flow.

Note: Address and Data bus in both 8088/8086 uses Multiplexed pins.

Pin-33: of 8088 and 8086 accepts maximum and minimum mode to select the processors operating mode.

Pin-28: outputs memory input/output of (M/IO) for 8086 and (IO/M) for 8088 to control interfaces between the CPU,I/O and memory devices.

Pin-25: controls Address Latch Enable (ALE) to indicate the valid physical address is present inside the address bus.

Pin-32: In min mode to control the data reading process of the microprocessor.

Pin-29: In min mode to control the data writing process.

Pin-27: To control the direction of data transfer mode.

Pin-34: To indicate if code or data is accessed during the ongoing bus-cycle.

Pin-22: Enhances the compatibility between high speed CPU with relative slower peripheral devices.