EL21C COURSE TEST #2

TUESDAY 25th NOVEMBER 2003

MICROPROCESSORS I

Time: (2:00 - 3:00 )PM

( 1 ) Sketch the serial waveform of the ASCII character ‘9’ (39H). Use 8 data bits, 1 stop bit,

and one parity bit of your choice. If the baud rate is 56.6K, approximately how many

characters are transmitted in a burst of 5 seconds ? [6]

( 2 ) Given an A/D Converter with the specifications below, sketch how you would interface it

to the SDK85 kit, then write an a subroutine (Take_reading) that takes a reading of the

analog voltage on the input and return the reading in the C-register (state any assumptions made).

Specifications: 8-bit A/D

10 mS conversion

(0-5VDC) input [8]

( 3 ) An 8-bit D/A Converter is interfaced to Port 00H of the SDK85 kit. Write a routine that

will produce the waveform below: [5]

( 4 ) Memory location 2000H contains a byte of data you wish sent out via the serial pin, SOD.

Write a program that will accomplish this task. [5]

( 5 ) The Timer on the 8155 IC must generate a square wave of 10KHz. The input clock frequency is

3-MHz. Explain how this is done and write code to accomplish this task. [6]

( 6 ) Write a short 8085 assembly language program (mnemonics and comments) that will

save the B-register on the Stack, if both Bit 0 & Bit 1 (of Reg.B) are Set, otherwise,

leave them alone. [5]

Bonus mark:

My Office Hours are posted on my Office door....what are they ??????

Maximum mark = 35