# Binary numbers

1. a) Perform the following binary subtractions of unsigned binary numbers. Convert your answer to decimal.

2
b) Repeat above but for when the binary numbers are in two’s complement form. Comment on the results.
Indicate whether or not the sum overflows an 8-bit result.

3. Shown below are the contents of a 16-bit resister. Determine the decimal value represented by the binary number if:

a) the binary number is unsigned
b) the binary number is in two’s complement form.

4. FIGURE 1 shows how a 3 to 8 line decoder (74138) can be used in conjunction with NAND gate (74133) to connect a set of switches to the data bus of a microprocessor system via buffers
(74367). Answer the following questions relating to the diagram:

a) What address, in HEX, is required on the address bus in order to read the switches?
b) RD and MEMRQ are control lines from the CPU. What must their logic state be in order to read the switches?

5. This question refers to the C68MX11 CPU, details of which accompany this assignment.

a) With reference to the block diagram of the CPU, what is the purpose of the CCR?
b) Again with reference to the block diagram, outline how the processor would add two numbers held in ACC.A and ACC.B the result being stored in memory. Identify the addressing modes that would be employed in this addition.
c) Give the address range in hex that the PC could access.

6. Three widely used but quite different processors are Intel & ARM and Atmel’s AVR.

Briefly contrast the architecture of these processors and how this relates to their application niche.
1. a) Perform the following binary subtractions of unsigned binary numbers. Convert

i) 100110012 – 010001002

ii) 110100102 – 101101102

b) Repeat above but for when the binary numbers are in two’s complement form.
Comment on the results.

c). Add the following additions of unsigned hexadecimal numbers. Indicate whether or not the sum overflows an 8-bit result.

a) 0716 + 0916
b) 1316 + 2816
c) AB16 + 3E16