EL-148 (PCC) Microprocessors Chapter 2

What two groups are the 16-bit address bus and 8-bit data bus split into?

(1) A8 to A15: output; three-state higher-order address bus (2) AD0 to AD7: input/output; three-state multiplexed address/data bus

What are the six groups of signals in the Intel 8085 microprocessor?

(1) Address bus, (2) Data bus, (3) Control and status signals, (4) Power supply and system clock, (5) Externally initiated signals, (6) Serial I/O signals

What are the components of the central processing unit?

(1) Arithmetic and logic unit (ALU), (2) control unit

What are the five functional units of the Intel 8085 microprocessor?

(1) Arithmetic and logic unit, (2) General-purpose registers, (3) Special-purpose registers, (4) Instruction register and decoder, (5) Timing and control unit

What are the three types of buses?

(1) address bus, (2) data bus, (3) control bus

What are the three functional blocks of the microprocessor system?

(1) central processing unit (CPU), (2) input and output units, (3) memory units

What is the clock frequency in the Intel 8085 microprocessor?

3 MHz

How many pins are on the Intel 8085 microprocessor?

40 pins

How many bits is the Intel 8085 microprocessor?

8 bits

In the Intel 8085 microprocessor, which 8-bit register is a part of the ALU and is the most important register? It is used to store 8-bit data and to perform arithmetic and logical operations.

Accumulator. The output of an operation is also stored within this register. The Intel 8085 microprocessor communicates with input/output devices only through this register.

What is the one-way bus that carries addresses from the microprocessor to the memory or other devices? It is a group of 16 one-directional lines that allows the flow of address from the processor to its peripheral devices.

Address Bus. Its basic function is to identify a peripheral or memory location.

Which output control signal indicates availability of a valid address on the multiplexed address/data lines, and occurs during the 1st clock cycle of a machine state, and enables the address to be stored in a latch or register, can be used to strobe the status information, and is never tri-stated?

Address Latch Enable (output)

This bus carries the binary number (i.e., the address) used to access a memory location. Binary data can then be written into or read from the addressed memory location. This bus consists of 16 wires and can, therefore, handle 16 bits.

Address bus

Which flag is set when an auxiliary carry is generated during an arithmetic operation in the accumulator, i.e., when a carry results from bit D3 and passes on to D4. This carry is also called half-carry. It may also occur in the process of a subtraction operation.

Auxiliary carry flag (AC). In other words, this flag is set if the subtraction operation results in borrow.

How are the registers in the Intel 8085 microprocessor combined as pairs to perform 16-bit operations?

B and C, D and E, H and L

What are the general-purpose registers in the Intel 8085 microprocessor?

B, C, D, E, H, and L

This is a group of conducting lines that carry data, address, and control signals.

Bus

What pin is used to provide the clock signal to the rest of the system?

CLK (output)

Which flag is set when a carry is generated in the process of an arithmetic operation in the accumulator? During addition, it sometimes results in a 9th bit being carried over 2 the next byte. This flag copies the value of the carry from D7 and reflects the value of the borrow in subtractions.

Carry flag (C)

This determines how many instructions per second the processor can execute. It is specified in megahertz (MHz)

Clock Speed

What is the bus that typically consists of a number of single lines that coordinate and control microprocessor operations? These individual lines provide a pulse to indicate the operation of the microprocessor. What bus is this referring to?

Control Bus

This bus has various lines for coordinating and controlling microprocessor operations. For example, RD and WR lines.

Control bus

This is used to take control of the system bus by placing a high signal on the Hold pin.

DMA controller

What is the two-way bus that carries data around the system? This bus is used for transfer of binary information between the microprocessor, memory, and peripherals.

Data Bus

This bus carries data in binary form between the microprocessor and external units such as memory. Typical size is eight or 16 bits.

Data bus

This flip-flop is used to store information about the status of the processor and the status of the instruction executed most recently.

Flag

In the Intel 8085 microprocessor, which register is quite independent, has each bit as a part of a single binary byte value and hence each bit has a numerical value? It is an 8-bit register and is used to indicate the status of a recent arithmetic or logical operation.

Flag register. The three remaining registers (D1, D3, and D5) are don't cares. Also, in this register, its bit is said to be "set" when its value is 1 and "cleared" when its value is 0.

Which two registers, when combined, are also used for memory-related instructions in the Intel 8085 microprocessor?

H and L

These signals are used for direct memory access (DMA) type of data transfer. The Hold request makes the 8085 drive all its tri-stated pins to high impedance state. This signal goes high to acknowledge the receipt of the Hold signal.

Hold and HLDA

Which control signals indicate whether the read/write operation is being done with respect to the memory or an I/O device? Logic 1 indicates I/O device access and logic 0 indicates memory access.

IO/M (output; three-state). This signal is tri-stated during hold and halt modes.

This 8-bit register usually temporarily stores the instructions drawn from memory locations, before their actual execution. The content of this register is decoded by the decoder circuitry, where the nature of the operation to be performed is decided.

Instruction Register and Decoder. In addition, there are two temporary registers W and Z, which are controlled internally and not available for user access.

Which flag of the flag register (within the Intel 8085 microprocessor) is set if the content of the accumulator after an arithmetic operation has an even number of 1s. Otherwise, this flag is reset. It is set for operation in the even parity mode. Which flag is this?

Parity flag (P)

What is the 16-bit register that always points to the address of the next instruction to be executed. After execution of every instruction, the content of the memory location indicated by this register is moved to the instruction register and this register is loaded with the next address.

Program Counter (PC). In other words, this register is used to sequence the execution of the instructions. This register keeps track of a program by counting the memory address from which the next byte is to be fetched.

Between RAM and ROM, which one is required in any system to store temporary programs and data?

RAM

Between RAM and ROM, which one is necessary to store fixed programs?

ROM

This is an input signal to the processor. It is used by the memory or I/O devices to get extra time for data transfer or to introduce wait states in the bus cycles.

Ready

Which control signals of the Intel 8085 microprocessor are used to indicate the kind of operation performed?

S0, S1 (output)

Of the two signals that implement serial transmission, which one has a line of bit data that is loaded in the seventh bit of the accumulator whenever a RIM instruction is executed?

SID (input)

Of the two signals that implement serial transmission, which one is set or reset as specified by the SIM instruction?

SOD (output)

What are the two signals that implement serial transmission?

Serial Input Data (SID), and Serial Output Data (SOD)

Which flag of the flag register is just a copy of the bit D7 of the accumulator? A negative number has a 1 in bit 7 and a positive number has a 0 in 2's complement representation. This flag indicates the sign of the number and can be used in signed arithmetic operations.

Sign flag (S)

Which register is an array of memory locations organized in last-in, first-out or first-in, last-out fashion? It is accessed by a 16-bit pointer register holding the address of the memory location of the top of the stack. This register stores return addresses of the main program in a subroutine.

Stack Pointer (SP). Care must be taken by the programmer to ensure that the data stored in this register is retrieved properly, so that the data stored in the register by the processor is not affected.

This unit gets commands from the instruction decoder and issues signals on the data bus, address bus, and control bus. What unit is this?

Timing and Control Unit

This is a non-maskable interrupt of the 8085 and is not disabled by processor reset after reorganization of interrupt.

Trap

To run the microprocessor at 3 MHz, a 6 MHz crystal should be connected to what pins?

X1 and X2

Which flag of the Flag register (within the Intel 8085 microprocessor) is set if an arithmetic operation results in a zero? It set's, i.e., it changes to binary 1 if the result in the accumulator is zero; if not, it remains reset, i.e., at binary 0. Which flag is this?

Zero flag (Z)

It is an 8-bit register; it is a part of the ALU and is the most important register. It is used to store 8-bit data and to perform arithmetic and logical operations. The output of an operation is also stored in this register. This register is identified as register A. What register is this?

accumulator

What are the special-purpose registers of the Intel 8085 microprocessor?

accumulator, flag register, program counter (PC), and stack pointer (SP)

Which registers are only used to store data that is being used by the program under execution and the results obtained from it?

general-purpose registers

Where are the results of the arithmetic and logical operations stored in the Intel 8085 microprocessor?

in the accumulator

How many bits can a flip-flop store at a time?

only one

What is a collection of eight D-type flip-flops with parallel-in and parallel-out operations?

register

What is another name for general-purpose registers?

scratchpad registers

What is the function of the arithmetic and logic unit?

to perform arithmetic and logical operations