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Overview of Eight-Bit Microprocessors
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Today, we will explore three significant eight-bit microprocessors. Can anyone tell me what an eight-bit microprocessor means?
I think it means it processes data in 8-bit chunks?
That's correct! Eight-bit microprocessors can handle 8 bits at a time. Let's dive into the first one: the Intel 8085. Does anyone know anything about it?
Doesnβt it have a specific pin configuration?
Yes, it does! The 8085 microprocessor features a 40-pin layout, essential for its connectivity. Remember the acronym VHOLDS for the important pins: Vcc, HOLD, RESET, etc. Can anyone find the function of the reset pin?
It sets the program counter to zero?
Exactly! Good job! Now, letβs summarize. The 8085 has a pin configuration that includes the Vcc for power and a reset pin to initialize its function.
Registers of 8085
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Now that we've discussed the pin configuration, let's look at the registers present in the 8085. Can anyone name a few registers?
Iβve heard of the accumulator?
Correct! The 8085 features an eight-bit accumulator and flag register, allowing it to perform arithmetic and logical operations. What do you think the flag register is used for?
It's for indicating the status of operations, right?
Right on! It has five flags for different conditions. So, remember: the flags help in knowing the outcomes of operations. Let's keep going with its data storage capabilities.
Addressing Modes of 8085
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Next, we will cover addressing modes. 8085 has four addressing modes. Who can give me one of them?
Isn't one of them direct addressing?
Yes! Direct addressing mode enables direct addressing of memory. Can anyone explain another mode?
I think register indirect addressing is one?
Exactly! Registers can hold the address of the data, which can be very efficient. Remember: Direct, Indirect, Register, and Immediate mode are the four types of addressing modes in the 8085.
Instruction Set of 8085
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Now, let's move to the instructions the 8085 can execute. An instruction is a binary code that tells the processor what operation to perform. Can anyone recall how many cycles it takes for an instruction to execute?
Is it between 1 to 6 machine cycles?
Correct! That's an important concept. Each machine cycle consists of T-states, indicating how the clock cycle is subdivided for processing. So, remember: an instruction cycle can vary in length based on operations.
Motorola 6800 and Zilog Z80 Overview
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Finally, letβs compare the Motorola 6800 and Zilog Z80. Who remembers a critical feature of the 6800?
It doesn't have I/O instructions, right?
Exactly! The 6800 uses memory-mapped I/O, a detail that's crucial for its operation. How about the Z80, anyone remember its key highlight?
It's compatible with the Intel 8080?
Correct! It has a broader range of instructions, with a total of 158. This makes it versatile in many applications. Remember: the unique features of each processor shape their applications in computing.
Introduction & Overview
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Quick Overview
Standard
The section outlines the architecture, pin configurations, registers, addressing modes, and instruction sets of three prominent eight-bit microprocessors: Intel 8085, Zilog Z80, and Motorola 6800, highlighting their unique features and compatibility.
Detailed
Eight-Bit Microprocessors
This section discusses the essential aspects of eight-bit microprocessors, particularly focusing on the Intel 8085, Zilog Z80, and Motorola 6800 models. It details their architectural layout through block diagrams and pin configurations, as well as their registers, addressing modes, and comprehensive instruction sets.
Key Points:
- 8085 Microprocessor:
- Pin Configuration: Provides insights into its 40-pin layout including essential pins like Vcc, HOLD, RESET OUT, etc.
- Registers: Describes its fundamental elements such as the accumulator, flag register, and pairs of 16-bit registers including BC, DE, and HL.
- Addressing Modes: Explains four modes: register addressing, register indirect addressing, direct addressing, and immediate addressing.
- Instruction Cycle: Elaborates on the execution of instructions, defined as an instruction cycle ranging from 1-6 machine cycles.
- Motorola 6800 Microprocessor:
- Describes its internal architecture, including key registers such as AC, SP, IX, and condition code registers.
- Identifies various addressing modes offered by the 6800, including implied, accumulator, immediate, direct, extended, relative, and indexed modes.
- Outlines a set of 72 core instructions related to data movement, arithmetic, logic, and control flow operations.
- Zilog Z80 Microprocessor:
- Emphasizes its compatibility with the Intel 8080, making it a versatile choice in industry-standard configurations.
- Details key registers like the accumulator, flag register, and the additional registers that enhance its functionality.
- Lists the expansive instruction set featuring 158 instructions, highlighting operations related to data transfer, arithmetic, logic, branching, and control operations.
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Introduction to Eight-Bit Microprocessors
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This section describes the block diagram, pin-out diagram, salient features and instruction set of the most popular eight-bit microprocessors, namely 8085 of Intel, Z80 of Zilog and 6800 of Motorola.
Detailed Explanation
This introduction lays the foundation for understanding the three main eight-bit microprocessors discussed in this section. The 8085, Z80, and 6800 are among the age-old microprocessors that have shaped digital electronics. Each microprocessor comes with its own architecture, features, and instruction set, making them distinct from one another.
Examples & Analogies
Think of these microprocessors like different brands of smartphones. Each brand has unique features and user interfaces but serves the same primary purpose of enabling communication, just like how these microprocessors execute instructions in computing.
8085 Microprocessor Overview
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Figure 13.11 gives the pin-out configuration and Fig. 13.12 shows a block diagram of the 8085 microprocessor. Table 13.3 lists the pin details.
Detailed Explanation
The 8085 microprocessor's design includes a configuration of pins that facilitate its functionality, which can be viewed in the visual representations provided in the figures. The pin-out configuration describes how the pins are laid out and what each pin is responsible for. The block diagram further illustrates the internal architecture of the 8085, showing how different components, such as the ALU, registers, and buses, connect and interact with each other.
Examples & Analogies
Imagine a multi-functional kitchen appliance, like a blender that can chop, mix, or blend. Each of these functions relies on specific controls and mechanisms within the appliance, just like the pins and components in the 8085 microprocessor control its various functions.
8085 Registers
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The 8085 microprocessor registers include an eight-bit accumulator, an eight-bit flag register (five one-bit flags, namely sign, zero, auxiliary carry, parity, and carry), eight-bit B and C registers (which can be used as one 16-bit BC register pair), eight-bit D and E registers (which can be used as one 16-bit DE register pair), eight-bit H and L registers (which can be used as one 16-bit HL register pair), a 16-bit stack pointer and a 16-bit program counter.
Detailed Explanation
Registers are small storage locations within a microprocessor that hold data temporarily during processing. The accumulator is regularly used for arithmetic and logic operations. The flag register keeps track of the conditions of the operations performed, such as if the result is zero or if there was a carry. The B, C, D, E, H, and L registers can be grouped together to create larger data storage units (16-bit pairs), allowing for more complex operations to be executed.
Examples & Analogies
Consider a library where the small registers are like individual bookcases. Each bookcase holds a handful of books (data) that can be accessed quickly. When working on a project (computation), you can take out multiple books from different bookcases as needed to develop your ideas efficiently.
Addressing Modes of the 8085
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8085 has four addressing modes. These include register addressing, register indirect addressing, direct addressing mode and immediate addressing mode.
Detailed Explanation
Addressing modes determine how the microprocessor accesses data. In register addressing, data is directly accessed from the registers. Register indirect addressing uses the content of a register as a pointer to data stored elsewhere. Direct addressing involves specifying the exact memory address to retrieve data, whereas immediate addressing uses constant values embedded in the instructions.
Examples & Analogies
Think of a classroom scenario: if a student wants to refer to a specific book (direct addressing), they go straight to it (memory). If they ask a friend (register indirect addressing), they get the location of the book instead. When a student uses notes theyβve written (immediate addressing), they refer to the content directly rather than going through the library.
8085 Instructions
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An instruction is a binary pattern designed inside a microprocessor to perform a specific function. The entire group of instructions a microprocessor can perform is referred to as its instruction set. An 8085 instruction cycle consists of 1β6 machine cycles. A machine cycle is defined as the time required to complete one operation of accessing memory, I/O, and so on. This will comprise 3β6 T-states, which is defined as one subdivision of the operation performed in one clock period.
Detailed Explanation
Instructions are the commands that tell the microprocessor what to do. The instruction cycle is the process that the microprocessor follows to execute a command, which can vary in length depending on the complexity of the instruction. Each part of the instruction cycle (machine cycles and T-states) represents different timing phases and operational tasks involved in fetching or executing instructions.
Examples & Analogies
Consider a cooking recipe as an analogy: following each step (instruction) in a recipe requires different amounts of time and effort (instruction cycle) depending on what youβre making. For instance, boiling water may take less time (1 machine cycle) than baking a cake (6 machine cycles) because it has more steps (T-states).
Motorola 6800 Microprocessor Overview
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This is an eight-bit microprocessor housed in a 40-pin dual in-line package (DIP) and released at the same time as Intel 8080. An important feature of 6800 is that it does not have I/O instructions, and therefore 6800-based systems had to use memory-mapped I/O for input/output capabilities.
Detailed Explanation
The Motorola 6800 microprocessor is notable for its design and features. Unlike some of its competitors, it does not contain dedicated I/O instructions. Instead, it relies on memory-mapped I/O, which means that devices are accessed as if they were memory locations. This required different design considerations for systems built around the 6800.
Examples & Analogies
Imagine a computer without a dedicated printer port, forcing you to send print jobs through a regular file system route instead. Each operation must be treated like storing files, making it less direct but flexible.
6800 Registers and Addressing Modes
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The 6800 microprocessor has six internal registers, namely accumulator A (ACCA), accumulator B (ACCB), an index (IX), a program counter, a stack pointer (SP) and a condition code register. It has the implied addressing mode, accumulator addressing mode, immediate addressing mode, direct addressing mode, extended addressing mode, relative addressing mode, and indexed addressing mode.
Detailed Explanation
Similar to the 8085, the 6800 also utilizes a series of registers to manage data. Its addressing modes give it the flexibility to operate on data stored in different ways, either directly using the values or using pointers to access them elsewhere, which adds versatility in programming.
Examples & Analogies
Think of a chef with multiple tools at their disposal (registers) who can follow various techniques (addressing modes) to create a dish. They can directly grab ingredients (direct addressing), refer to their notes for quantities (immediate addressing), or use the inventory system to find what they need quickly (indirect addressing).
Zilog Z80 Microprocessor Overview
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The Zilog Z80 microprocessor is an eight-bit processor that is object-code compatible with Intel 8080. It is available in industry-standard 40-pin dual in-line and 44-pin chip carrier packages. The maximum operating frequency is 2.5MHz.
Detailed Explanation
The Z80 offers a powerful architecture compatible with the earlier Intel 8080, making it easy to transition for developers. Its design allows for high processing speeds, accommodating a variety of applications which contributed to its popularity.
Examples & Analogies
Think of the Z80 like a new version of an existing smartphone compatible with all your previous apps (Intel 8080 code). You can enjoy faster processing (2.5 MHz) while still having access to all the features you were already familiar with.
Z80 Registers and Instruction Set
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The Z80 microprocessor has registers compatible with the 8080 microprocessor as well as some other registers. The 8080-compatible registers include the accumulator, flag register (F), general-purpose registers (six programmable general-purpose registers designated B, C, D, E, H, and L), stack pointer (SP), and program counter. The registers introduced with Z80 are the alternate accumulator register (A'), the alternate flag register (F'), the alternate B, C, D, E, H, and L registers (represented as A', B', C', D', E', H', and L'), the index registers (IX and IY), the interrupt vector register (I), and the memory refresh register (R). The Z80 microprocessor has 158 instructions.
Detailed Explanation
The Z80 expands on the concepts of registers used in the 8080, offering a wider variety for handling data. By providing alternate registers, it allows more complex operations without the need to overwrite values in memory. The extensive instruction set (158 instructions) enhances its programming capabilities, making it a versatile option for various applications.
Examples & Analogies
Imagine upgrading from a basic toolbox to a professional-grade one that not only includes more tools but also has duplicates for quick projects. This avoids the hassle of putting something down and makes it easier to switch tasks without losing track.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Intel 8085 Architecture: It features a 40-pin layout and contains various registers crucial for operations.
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Motorola 6800 Limitations: Not having dedicated I/O instructions requires the use of memory-mapped I/O.
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Zilog Z80 Compatibility: It boasts compatibility with the 8080 while extending its functionality with more instructions.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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The Intel 8085 is often used in educational settings to teach the basics of microprocessor architecture.
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Motorola 6800 is utilized in embedded applications where simple microcontroller functions are needed.
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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In an 8085's grand design,
π Fascinating Stories
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Imagine a factory where each machine is a register operating on numbers. The flag register is like the supervisor, checking if each machine is functioning correctly and reporting any errors.
π§ Other Memory Gems
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Use the acronym 'ARFM' to remember key registers in 8085: Accumulator, Register Flag, Memory address.
π― Super Acronyms
Remember 'IPRM' for instruction cycles
- Instruction
- Process
- Read
- Memory.
Flash Cards
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Glossary of Terms
Review the Definitions for terms.
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Term: Accumulator
Definition:
An eight-bit register in a microprocessor used for arithmetic and logical operations.
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Term: Flag Register
Definition:
A register that indicates the status of operations conducted by the processor, containing various flags.
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Term: Machine Cycle
Definition:
The time required to complete one operation of accessing memory or I/O.
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Term: Instruction Cycle
Definition:
The total time needed to execute an instruction, which can involve multiple machine cycles.
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Term: Addressing Mode
Definition:
A method to specify where the operand is located in memory or registers.