Unit5test

test

The microprocessor on which our hypothetical model and the ET-3400 are based in the ____ MPU

6800

The major difference in our hypothetical model and the 6800 MPU is that the latter has two ____

Accumulators

The program counter in the 6800 MPU has ___ bits

16

How wide is the address bus in a 6800-based microprocessor

16 bits wide

What is the range of address in the 6800 MPU

Addresses from 0000 to FFFF or 0000 to 65,535

List the six code flags

C, V, Z, N, I, H

carry, borrow

overflow

Zero

Negative

Interrupt mask

Half carry

Besides the program counter, what other 16-bits register are used in the 6800 MPU

Index register and stack pointer

In the 6800 MPU, does each accumulator have its own carry flag

No, the two accumulator share a common carry flag

list the seven general categories of instructions

Arithmetic, data holding, logic, data test, index register and stack pointer, jump and branch, condition code.

What is meant by the shorthand notation: A + B → A

This notation indicates that the value of B is added to A: transfer the result to accu Aand overwrite its original value.

How is the flag “C” affected by the “ADD” and “add with carry” instructions?

The C flag is set if a carry occurs, it is cleared otherwise.

Is the C flag changed when the AND instruction is executed?

No, C flag is unaffected by “AND” instruction

Explain the difference between the NEG instruction and the COM instruction.

COM replaces operand with its 1’s complement while NEG replaces it with its 2’s complement.

Explain the difference between the ANDA instruction and the BITA instruction

ANDA instruction places the result of AND operation in accu A. while BITA, the condition code register are set according to the result, but the result is not retained

The decimal adjust instruction is associated with which accumulator

Decimal adjust instruction works only with ACCU A

When the RORA instruction is executed the LSB of accu A is shifted into the ____ register

Carry

List eleven operation that can be performed directly to an operand in memory without first loading it into one of the MPU registers.

A byte in memory can be; cleared, incremented, decremented, complemented, negated, rotated left, rotated right, shifted left arithmetically, shifted right arithmetically, shifted right logically and tested.

Explain the difference between the SUBB instruction and the CMPB instruction

With the SUBB instruction, a difference is produced and placed in ACCU B. with CMPB, a flag is set as if a difference is produced but the difference is not retained.

List four types of logic operations that the 6800 MPU can perform

Complement, AND, inclusive OR, and Exclusive OR

When the LDX instruction is executed, from where is the index register loaded

The upper half of the index register is loaded from the specified memory location, the lower half from the byte following the specified memory location.

List four conditional branch instruction that are commonly used after a compare or subtract instruction to compare 2’s complement numbers.

BGE, BGT, BLE, BLT

Explain the difference between BGT and BBHI instructions

BGT is used to test the result of subtracting 2’s complement numbers. BHI is used to test the result of subtracting unsigned numbers.

What instruction is commonly used to fill a hole left in a program after an unwanted byte is removed?

NOP

Which instruction in the 6800 roughly correspond to the halt instruction in our hypothetical machine

WAI

Which of the condition code can be individually set or cleared?

C, I, V

When you have doubt as to exactly what operation is performed by a given instruction, where you can look to find the answer

Appendix A of this course

A disadvantage of direct addressing is that the operand must be in the first ___ bytes of memory

256

The advantage of direct addressing is that only ___ bytes are required for each instruction.

TWO

Extended addressing can address ___ bytes of memory

65, 536

A disadvantage of extended addressing is that each instruction requires ____ bytes

Three

Can extended addressing be used to address an operand in the first 256 bytes of memory

Yes, direct addressing is normally used when operand is in the first 256 bytes of memory but extended addressing can also be used.

The most powerful addressing mode available to the 6800 is called ____ addressing

Indexed

Indexed addressing requires _____ bytes for each instruction

two

The second byte of the indexed addressing instruction is called the ____ address

Offset

How is the address of the operand determined when indexed addressing is used

The offset address is added to the contents of the index register

How many MPU cycles are required by the INC, X instruction

Seven

How many bytes in the LDS # instruction

Three