Minimum Mode in the 8086 Microprocessor

In this tutorial, we will learn about the minimum mode of the 8086 Microprocessor, and will also learn the various PINs which work in minimum mode. By Monika Sharma Last updated : May 16, 2023

There are two modes of the 8086 microprocessor. The pin 33 decides whether the processor will work in minimum mode or maximum mode. If the pin is set, then the minimum mode is followed, else the processor works in maximum mode.

The pins from 24 to 31 are multiplexed in such a way that they work differently in these two modes. Let us first discuss the working of these pins in minimum mode.

Minimum Mode PINs

HOLD

This is a control signal sent by the connected external peripheral device to acquire the microprocessor buses. What this means is that is an external device like the input and output devices are connected to the 8086 microprocessor and they require the control over the buses, then a HOLD signal is sent by that device at this pin.

HLDA

After the control of buses is transferred to the external peripheral device, then an acknowledgment signal is sent for the same through this pin.

WR'

This signal is used for writing purpose. It is an active low signal.

M / IO'

This pin tells whether the operation is performed in the memory or through the IO devices. If this pin is 1, then the operations are performed in memory, else in the IO devices.

DT / R'

This signal tells whether the data is transferred or received. The microprocessor transfers the data when the pin is at 1, and at 0, it receives data.

DEN'

DEN stands for Data Enable. This pin is used to activate a chip in case of multiple chips. It is an active low signal.

ALE

This pin is used to Latch address from multiplexed bus to temporary storage in the 8086 microprocessor. If this pin is set to high, then the AD0 to AD15 pins will carry address, else they will carry data in them.

INTA

INTA stands for interrupt acknowledgment. If an interrupt request is received at INTR, then the acknowledgment for it is sent through this pin.

The CALL and RET Instruction in the 8086 Microprocessor

Maximum Mode in the 8086 Microprocessor