Read Interrupt Mask Instruction In 8085 | RIM Instruction In 8085 Microprocessor

Summary

This tutorial introduces the RIM (Read Interrupt Mask) instruction in the 8085 microprocessor, explaining its role in managing interrupts. RIM disables specific interrupts by reading their status, represented by bits in the accumulator. The video clarifies the function of each bit, including the interrupt enable (IE), pending interrupts (RST 7.5, RST 6.5, RST 5.5), and the serial input data (SID). It emphasizes the importance of understanding which interrupts are enabled, pending, or masked for effective microprocessor operation. Stay tuned for the next video on the SIM (Set Interrupt Mask) instruction.

Takeaways

• 📘 The full form of RIM is 'Read Interrupt Mask', which is used to disable interrupts.
• 😷 Masking interrupts is akin to wearing a face mask, covering them to prevent their effect.
• 🔢 The RIM instruction reads the status of three interrupts: RST 7.5, RST 6.5, and RST 5.5.
• 🛑 An interrupt is considered 'masked' or disabled if its corresponding bit in the RIM register is set to 1.
• 👀 The lower order three bits of the RIM register represent the status of the interrupts.
• 💡 The IE (Interrupt Enable) bit, located at D3, controls whether interrupts are enabled or disabled.
• 🚨 The three bits at D4, D5, and D6 represent the pending status of the RST 7.5, RST 6.5, and RST 5.5 interrupts, respectively.
• 🔝 The most significant bit, D7, represents the Serial Input Data (SID).
• 🔄 After executing the RIM instruction, the status of interrupts and SID is loaded into the accumulator.
• 📊 The accumulator can then be used to determine which interrupts are pending, enabled, or masked.
• 👋 The next tutorial will cover the SIM (Set Interrupt Mask) instruction, which is used to set which interrupts are masked.

Q & A

What does RIM stand for in the context of microprocessors?

RIM stands for Read Interrupt Mask. It is an instruction that reads the status of interrupts in a microprocessor.

What is the purpose of the RIM instruction in microprocessors?

The RIM instruction is used to read the status of various interrupts, such as whether they are enabled, masked, or pending, and the serial input data.

How does the RIM instruction relate to interrupt handling in microprocessors?

The RIM instruction helps in understanding which interrupts are enabled, which are masked (disabled), and which are pending, allowing for proper interrupt handling.

What does the term 'masking' mean in the context of interrupts?

Masking interrupts means disabling them. In the context of the RIM instruction, if an interrupt is masked, it will not be processed.

What are the three interrupts mentioned in the script, and how are they represented in the RIM instruction?

The three interrupts mentioned are RST 7.5, RST 6.5, and RST 5.5. They are represented by the lower order three bits of the data read by the RIM instruction.

How can you determine if an interrupt is enabled or disabled using the RIM instruction?

By examining the accumulator after executing the RIM instruction, if the bit corresponding to an interrupt is 1, it means the interrupt is masked (disabled). If it is 0, the interrupt is enabled.

What does the IE bit represent in the RIM instruction, and how does it affect interrupt processing?

The IE bit, represented by D3 in the accumulator, stands for Interrupt Enable. If IE is set to 1, interrupts will be enabled for processing; if it is 0, they are disabled.

What does it mean for an interrupt to be 'pending'?

An interrupt is considered 'pending' if it has occurred but has not yet been acknowledged or processed by the microprocessor.

How is the status of pending interrupts represented in the accumulator after the RIM instruction?

The status of pending interrupts is represented by bits in the accumulator. If a bit corresponding to an interrupt is set to 1, it indicates that the interrupt is pending.

What is the significance of the most significant bit (D7) in the accumulator after executing the RIM instruction?

The most significant bit (D7) represents the Serial Input Data (SID). It reflects the serial input data after the RIM instruction is executed.

What is the SIM instruction mentioned at the end of the script, and how does it differ from the RIM instruction?

The SIM instruction stands for Set Interrupt Mask. It is used to set or mask interrupts, whereas the RIM instruction is used to read the status of interrupts and serial input data.

Outlines

00:00

📘 Understanding the RIM Instruction

The first paragraph introduces the RIM (Read Interrupt Mask) instruction in the microprocessor tutorial series. It explains the full form of RIM as 'Read Interrupt Mask', emphasizing its function to disable interrupts. The tutorial discusses how RIM can be used to determine the status of three interrupts (RST 7.5, RST 6.5, and RST 5.5) by examining specific bits in an 8-bit data format. The paragraph also explains the concept of masking interrupts and how the RIM instruction helps in identifying whether interrupts are enabled or disabled, pending, or acknowledged. It touches on the significance of the IE (Interrupt Enable) bit and the role of the most significant bit (D7) as the Serial Input Data (SID). The summary concludes with the practical application of the RIM instruction, which is to load the status of interrupts and serial data input into the accumulator for further analysis.

05:02

🔍 Analyzing the RIM Instruction's Output

The second paragraph delves deeper into the RIM instruction's output, explaining how it provides insights into the status of interrupts and the serial data input. It clarifies that the RIM instruction loads the pending interrupts, interrupt masks, and the state of the serial input data into the accumulator. The paragraph illustrates how to interpret the accumulator's data to understand which interrupts are pending, enabled, or maxed (disabled). It also explains the significance of the least significant bit in determining which interrupt is maxed. The summary ends with an overview of the RIM instruction's purpose in the context of the 8085 microprocessor and teases the upcoming SIM (Set Interrupt Mask) instruction in the next video. The paragraph concludes with an invitation for viewers to ask questions, like, share, and subscribe to the channel.

Keywords

💡Microprocessor

A microprocessor is a central processing unit (CPU) integrated circuit that forms the brain of a computer, handling all the processing tasks. In the context of the video, it is the main theme as the tutorial series focuses on understanding microprocessor instructions, specifically the RIM (Read Interrupt Mask) instruction.

💡RIM (Read Interrupt Mask)

RIM stands for 'Read Interrupt Mask', which is an instruction used in the microprocessor to read the status of various interrupts. The video explains that RIM is used to determine which interrupts are enabled, disabled, or pending, and it loads this information into the accumulator for further processing.

💡Interrupt

In computing, an interrupt is a signal sent to the processor to temporarily suspend its current tasks and attend to a higher priority task. The video discusses how the RIM instruction reads the status of three specific interrupts (7.5, 6.5, and 5.5), which are crucial for understanding the microprocessor's operation.

💡Masking

Masking, in the context of interrupts, refers to the process of disabling certain interrupts. The video uses the analogy of wearing a face mask to explain how masking 'covers' or disables an interrupt, preventing it from being recognized by the microprocessor.

💡Accumulator

The accumulator is a register in a microprocessor used for arithmetic and logical operations. The video mentions that after the RIM instruction is executed, the status of interrupts and serial input data is written into the accumulator, allowing for further analysis of the interrupt status.

💡IE (Interrupt Enable)

IE stands for 'Interrupt Enable', which is a bit in the microprocessor's status register that, when set to 1, enables interrupts to be recognized and processed by the CPU. The video explains the role of the IE bit in determining whether an interrupt will be acknowledged and acted upon.

💡Pending Interrupt

A pending interrupt is an interrupt request that has occurred but has not yet been acknowledged or processed by the CPU. The video describes how the RIM instruction reveals which interrupts are pending by checking the status bits in the accumulator.

💡Serial Input Data (SID)

Serial Input Data (SID) refers to data that is received in a sequential manner, one bit at a time. The video mentions that the most significant bit in the accumulator after the RIM instruction represents the SID, indicating the status of the serial data input.

💡Instruction Set

An instruction set is the collection of all the basic instructions that a microprocessor can execute. The video is part of a tutorial series that aims to teach about different instructions in the microprocessor's instruction set, starting with the RIM instruction.

💡SIM (Set Interrupt Mask)

Although not the main focus of the video, SIM is mentioned as the next instruction to be covered in the series. SIM stands for 'Set Interrupt Mask' and is used to set or enable interrupts, contrasting with the RIM instruction that reads their status.

Highlights

Introduction to the microprocessor tutorial series.

Explanation of the RIM (Read Interrupt Mask) instruction.

RIM stands for Read Interrupt Mask, which is used to disable interrupts.

The concept of masking interrupts is compared to wearing a face mask.

Description of the three interrupts: RST 7.5, RST 6.5, and RST 5.5.

Explanation of how the RIM instruction reads the status of interrupts.

Details on how the lower order three bits represent the mask interrupts.

The function of the IE (Interrupt Enable) bit and its role in enabling interrupts.

Clarification of the meaning of pending interrupts and their representation by bits.

The significance of the most significant bit (D7) as the Serial Input Data (SID).

How the RIM instruction loads the status of interrupts and SID into the accumulator.

Understanding which interrupts are pending, enabled, or masked after the RIM instruction.

The practical application of the RIM instruction in microprocessor programming.

Upcoming tutorial on the SIM (Set Interrupt Mask) instruction.

Invitation for viewers to ask questions in the comment section.

Encouragement for viewers to like, share, and subscribe to the channel.

Transcripts

dear students i welcome you all to this

microprocessor tutorial series in this

video we will learn about the rim

instruction and in our upcoming video we

will learn about the sim instruction so

what is the full form of rhythm rim

stands for read interrupt max that means

whatever be the interrupt that is maxed

max meanings it is disabled so let me

write down here

masking means it is disabling disabling

means we are just covering something

suppose we are wearing a face mask that

means we are covering our face another

person are not able to see our face in

the case of microprocessor also when you

max some interrupts that means that

interrupt will be disabled using this

read interrupt marks we will know the

various status of the interrupts so here

we will see basically three interrupts

that is the rst 7.5 rsd 6.5 and rsd 5.5

here i have shown a 8 bit data suppose

from d 0

d 1 d 2

d 3 d 4

d5 d6 d7 so in the case of read

interrupt marks what will happen the

lower order three bits here these three

bits this one three these three bits

this will be having the

max interrupts so let me write down

first this is

7.5 this is 6.5 and this is for 5.5 this

is the rst 7.5 rsd 6.5 and rst 5.5 so

these are the marks interrupts okay so

let me write down here this is the marks

of

interrupts so when this interrupt will

be marked that will be dependent on

these bits so if this value is 1

if equal to 1

that means this is interrupt is mass

must means it is disabled that means

whenever we have suppose 1 0 0 that

means rst 7.5 is disabled other are

enabled so whenever we have one value

here that will represent that that

interrupt is maxed max means it is

disabled okay next we have the ie here

ie means let me write down here d3 bit

will represent the ie ie means interrupt

enable so what will be the function if

this is equal if this interrupt enable

equal to 1 whatever be the interrupt

here depending on the max that interrupt

will be functioning and if this equal to

0 then this is disabled 0 means disable

1 means enable at this interrupt enable

bit so this is the third bit okay next

we have d4 at d4 will be having a

interrupt

six enter 5.5 here i'll be having

interrupt

6.5 and

i

7.5 so what is the meaning of this three

interrupt whenever we have one value in

any of these interrupts suppose in some

cases all of this inter may be having

one value all of these bits having one

value that means the interrupt is

pending

if let me write down here if these

values equal to 1 that means that

interrupt is equal to pending that means

interrupt is not acknowledged this is

the meaning of these three bits and the

most significant bit that is d7 it will

represents as i d it will represent s id

s id means it is the serial input data

so whatever be the data that is serial

input that will be reflected here after

going through this instruction all the

status values suppose it may be having

0 0 1 0 1 0 0 1 suppose this is the

content of this interrupt status signals

so after going through this instruction

this data will be written into the

accumulator so after having the bits in

the accumulator then we can easily

understand which interrupt is pending

which interrupt is enabled or not if

there is a max interrupt or not so from

that we can easily understand so suppose

for this example only let me tell you

this most significant bit this will

represent the s id as id means it is the

serially input data so you need not to

bother about this next we have this one

is the distribution represents the

interrupt which is pending that means

this one was for the rst 7.5 this one is

for rst 6.5 this is for rst 5.5 so what

we understand from here that r s t the

second one this one rsv this one is

pending because this value this bit is

one therefore we can write rsd 6.5 is

pending so after reading the interrupt

status we can understand that the

restart or the rsd 7.5

interrupt is pending next we have this

one value one value means it is the

interrupt enable signal so if value if

this value is one that means interrupt

is enable that means it is interrupt is

enabled next we have these are the three

bits this three bit will represent which

interrupt is maxed so from here we can

say that the interrupt 5.5 is

maxed

why i'm writing here five point five

because the least significant bit is one

here if this one was one then what will

happen the interrupt six point five is

max if this value has been one then we

could have said that the interrupt 7.5

is maxed so in this way you have to

understand that in the case of rim

instruction what will happen this rim

instruction is used to read the status

of the interrupts that is 7.5 6.5 and

5.5 and the serial data input bits okay

so we have seen about this rim

instruction this instruction loads the

pending interrupts as well as the

interrupt marks as well as the restart

inter marks and the contents of the

serial input data into the accumulator

so after going through this instruction

this data will be written into the

accumulator okay this is all about the

rim instruction in 8085 in our upcoming

video we will see about the sim

instruction that is the set interrupt

max instruction thank you for watching

if you have any question please put it

in the comment section below also like

share and subscribe to my channel thank

you

[Music]

you