PROGRAMMABLE INTERFACE
CONTROLLERS
Understanding what PIC’s are.
How to use PIC logicator
Knowing what you can do with PIC
circuits
What a PIC does
PIC’s allow you to control output devices when they are triggered by sensors and switches.
Programs can be generated by using flowcharts within computer software, which can then be
downloaded into a PIC chip. They can be re-written as many times as you want. This type of
memory is called flash memory.
Inside the
PIC CHIP
A PIC microcontroller is a single
integrated circuit small enough to fit in the
palm of the hand and contains memory
processing units, a Clock and Input/
Output circuitry in a single unit. A PIC
microcontroller is ,therefore, often
described as a computer in an integrated
circuit.
PIC microcontrollers can be purchased
blank and then programmed with a
specific control program.
PIC microcontrollers can also be
purchased with a pre-programmed set of
commands that allows a direct cable
download from a computer and reduces
the cost of programming equipment.
Advantages/Dis-advantages of
PICs compared to a 555 Timer
flashing circuit (astable)
 PIC
allows greater control.
 Pattern can be tested on PC before build
 PIC can be programmed to produce
different patterns
 Limited output from 555 Timer IC
 PIC requires fewer components
 PIC more costly than 555
 PIC possibly smaller PCB
 PIC requires programming skills
PIC TASK (EXAM QUESTION)
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Using a programming system you
are familiar with, produce a
sequence of commands, which
would make a set of 4 LED’s,
shown in Figure 3, switch on as
shown below:
Next to each of the commands,
explain its purpose.
All four LED’s go high for 1
second.
A, B, C and D go high in sequence,
each for 0.25 seconds.
All four LED’s go high for 1
second.
D, C, B and A go high in sequence,
each for 0.25 seconds.
This repeats continuously.
Between each statement, all LED’s
go low for 0.25 seconds.
PIC TASK (EXAM QUESTION)
Use a PIC to simplify the electronic
circuit for a steady hand game
The PIC system diagram is shown below;
Use a PIC program to satisfy the
following conditions.
(a)
Each time the wand and track touch, the
PIC switches on an LED in the sequence
1, 2 and 3. Once an LED is lit it will stay
on until reset. (9 marks)
(b)
Once the wand and track touch, the PIC
will ignore any further contact between
the wand and track for 2 seconds. (4
marks)
(c)
On the loss of the third life, the buzzer
will switch on for 0.25s and then switch
off for
0.25s. This is repeated three times. (6
marks)
(d)
The PIC program will re-set back to ‘no
lives lost’. (3 marks)
PIC TASK
(EXAM QUESTION)
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The picture opposite shows a
drawing of a lift with its doors
open at the ground floor.
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The lift will only operate when a
person has requested the lift
from another floor, or a floor
has been chosen by a person in
the lift and the doorway is not
obstructed.

Design a flow chart to illustrate
the lift operating sequence,
from when the lift starts at the
ground floor, with its’ doors
open and is called to the first
floor where its doors open. (10
marks)
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Quality of drawing (2 marks)