In the Intel 8085 microprocessor, on what primary basis are hardware interrupts broadly classified when considering whether they can be disabled by software?

Introduction / Context:
This question addresses how interrupts are classified in the Intel 8085 microprocessor, specifically with reference to whether they can be disabled by software. The 8085 supports both maskable and non maskable interrupts, and this classification is important for understanding which events can be temporarily ignored and which must always be serviced. Such knowledge is essential when designing reliable embedded systems where some signals may be safety critical.

Given Data / Assumptions:

The context is the set of hardware interrupts in the 8085 microprocessor.

Some interrupts can be masked or disabled using software controlled bits.

At least one interrupt, TRAP, is designed so that it cannot be masked by ordinary software operations.

The question asks about broad classification based on ability to enable or disable interrupts.

Other classifications such as vectored versus non vectored exist, but they are not the focus here.

Concept / Approach:
In the 8085, hardware interrupts are commonly classified as maskable and non maskable. Maskable interrupts such as RST 7.5, RST 6.5, RST 5.5, and INTR can be enabled or disabled either globally using the interrupt enable flip flop or individually using the interrupt mask register. Non maskable interrupts such as TRAP cannot be disabled through these software mechanisms and thus are always recognized when asserted. This classification is extremely important for handling critical events that must not be ignored, such as power failure conditions assigned to TRAP.

Step-by-Step Solution:
Step 1: Recall that TRAP is a non maskable interrupt and the highest priority interrupt in the 8085.Step 2: Notice that RST 7.5, RST 6.5, RST 5.5, and INTR are maskable interrupts, which can be disabled using the EI and DI instructions and interrupt mask settings.Step 3: Recognize that this naturally leads to the classification of interrupts into maskable and non maskable categories.Step 4: Compare this classification with the answer options provided.Step 5: Select the option that explicitly states maskable and non maskable as the classification basis, rather than focusing on vector addresses or timing.

Verification / Alternative check:
Standard 8085 documentation includes a section on the interrupt system that clearly divides interrupts into two groups: maskable and non maskable. TRAP is described as non maskable, while the rest are described as maskable. Although other classifications such as vectored versus non vectored also appear in the literature, when the question emphasizes the ability to disable interrupts using software, maskable versus non maskable is the only correct answer. This matches the selected option and confirms its correctness.

Why Other Options Are Wrong:
Option A refers to vectored and non vectored interrupts, which is another valid classification, but it is based on whether the interrupt has a fixed vector address, not on masking. Option B describes synchronous and asynchronous timing but does not correspond to a standard 8085 classification in common exam questions. Option D talks about internal and external interrupts based on physical location, which is not the key distinction emphasized in 8085 textbooks. Option E distinguishes hardware and software interrupts, but software interrupts are generated by instructions like RST and are not the focus of this classification question.

Common Pitfalls:
Students often mix up different classification schemes and may quickly think of vectored versus non vectored when they see the word classify. Another pitfall is to confuse hardware versus software interrupts with maskable versus non maskable. To answer correctly, always pay attention to the phrase can be disabled by software, which points directly to the maskable versus non maskable distinction in the 8085.

Final Answer:
In the 8085, hardware interrupts are broadly classified as maskable and non maskable based on whether they can be disabled or enabled by software control.