Zoombak A-GPS Universal Locator Guia do Utilizador descarregar pdf (Página 22)

15 | P a g e

used for timing. The FSM and counter have a common clock signal with a 1 kHz frequency. The

control has 3 external inputs: Arm, Disarm, and the Accelerometer output. It also has 2 outputs:

Alarm enable and a reset for the accelerometer circuit. Due to the many different states

allowable with a PROM device, the device has to be programmed using a long truth table. We

have provided a logically simplified truth table for programming the PROM to work as the

combinational logic of the finite state machine.

C-3 Cost to Implementation Prototype

Control

Parts list prototype

Quantity

Vendor

Cost

7474 (dual D flip-flip)

on hand

$0.49

EPROM

on hand

$4.75

74161 (4-bit up counter)

on hand

$0.91

555 timing chip

on hand

$1.99

1k ohm resistor

on hand

$1.19

2k ohm resistor

on hand

$1.19

10k ohm resistor

on hand

$1.19

Printed circuit boards

Radioshack

$2.49

Destroyed boards

Radioshack

$2.49

Destroyed 74161

on hand

$0.91

Total

$17.60

Table C- 1 Break down of Prototype Cost for Control System

C-4 Time to Implement Prototype

1-2 weeks for designing schematic of controls

2-3 days for designing and simplifying truth table for PROM

1 day for construction of PROM circuit board

2-3 days for construction of clock

2-3 weeks for construction of counter

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 85 86

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