ELET2100 (EL21C) COURSE TEST #2

WEDNESDAY 23rd NOVEMBER 2005

MICROPROCESSORS I

Time: (12:00 - 1:00 )PM

( 1 ) Sketch the waveform (bit-stream) for the ASCII character (20H),

SPACEBAR, using serial transmission with 7-bit data, even parity, one stop

bit, at 128K baud rate. How long would it take to transmit the word:

ELECTRONICS [4+2]

( 2 ) Write Assembly Language (AL) code for the 8155 Timer on the SDK-85 kit in your Lab,

assuming the Clock Frequency in to the 8155 is 10 MHz, that will produce a continuous

square wave with a frequency of 1 KHz. Can this Timer produce a Frequency of 100 Hz ?

Explain your answer. [6+2]

( 3 ) The A/D converter below in Figure 1, require 11 port-bits to be fully under the control of

an SDK-85 kit from your Lab. Assume you only have Ports 00 and 01 at your disposal.

Show how you would interface the system and write AL code to take a reading and store

it in memory location 20A0H.

[8]

Figure 1:

( 4 ) On the A/D converter above, a temperature sensor with an output of 0 – 1.0 VDC

corresponds linearly to a temperature range of (20 – 40) ºC. What is the voltage &

temperature resolution ? If you read an output of 6FH, what voltage and

temperature would this indicate on Vin ? [6]

( 5 ) Assume that an Interrupt Service Routine (ISR) for interrupt TRAP is stored

in memory beginning at 2060H. Explain what sequence of steps must occur

for this ISR to be activated. [7]

Bonus mark:

Name any ONE of the THREE Secretaries in the Department of Computer Science,

Mathematics & Physics (First name, Surname....any will do !).

Maximum mark = 35