b$)\frac{?}{\text{b}\text{a}\text{r}}(RD)$ and $\frac{?}{\text{b}\text{a}\text{r}}(MEMRQ)$ are control lines from the CPU. What must their

logic state be in order to read the switches?

This question refers to the C$68$MX$11$ CPU, details of which

accompany this assignment.

a$)$ With reference to the block diagram of the CPU, what is the

purpose of the program stack and the accumulators $A,B$ and $D?$

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.

Three widely used but different processors are Intel, ARM

and Atmel's AVR.

Identify commonalities and contrast the architecture of these

processors and how this relates to their particular application niche.

a$)$ Describe the modes of operation of the Intel $8255$ Programmable

Peripheral Interface.

b$)$ The ASCII $7-$bit code for $\text{'}J\text{'}$ is $01001010.$ Express this as $8-$bit

even$-$parity code where the parity bit is the least significant.

c$)$APC$16550$D UART has a clock running at$18\mathrm{.}432$ MHz and its

baud rate is set to $2000.$Determine the HEX contents of its DLM and

DLL registers.

d$)$ Using the grid below, sketch a waveform to show how the data

$10101000$ would be transmitted to line using Non$-$return$-$to$-$zero

inverted $($NRZI$)$ line encoding. Assume the signal level is initially

high as shown.

a$)$ The diagram below shows the structure of a USB token packet.

Identify the function of each field

b$)$ Identify the four basic types of data transfers that are supported

by the USB architecture. Write a sentence on how each type is

used

c$)$ Identify which OSI model layers are relevant to both USB $2$ and

USB $3.$

d$)$ Outline three improvements offered by USB $3\mathrm{.}2$ compated to

USB$2.$Programmer's Model

Block Diagramsa$)$ Perform the following binary subtractions of unsigned binary

numbers. Convert your answer to decimal.

i$){10100101}_2-{01001001}_2$

ii$){11011010}_2-{10010011}_2$

b$)$ Repeat the calculations above but for when the binary

numbers are in two's complement form. Comment on the

results of the two methods used, noting and discrepancies.

Find the sums of the following unsigned hexadecimal numbers.

Indicate whether or not the sum overflows an equivalent $8-$bit

binary result.

a$){11}_{16}+{22}_{16}$

b$){17}_{16}+{35}_{16}$

c$)F{A}_{16}+C{E}_{16}$

d$)B{A}_{16}+A{B}_{16}$

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.

FIGURE $1$ shows how a $3$ to $8$ line decoder $($TTL $74138)$ can

be used in conjunction with NAND gate $($TTL $74133)$ to connect a

set of switches to the data bus of a microprocessor system via buffers

$($TTL $74367).$

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?