Nokia 7280 Service Manual

RM-14

Nokia Customer Care

7 - System Module

COMPANY CONFIDENTIAL

ISSUE 1 11/04

In the following:

-contacts in rotator are CAPITAL LETTERS

-pins on TIKU are corresponding lowercase letters (Thus switch A corresponds to pin A on
TIKU).

If the system has been initalized following routine is present (starting at point 1):

System has enabled pin c (driven low), a and b are disabled (pulled high).

Pos. 1: Contact A and B are closed, C is open (pin a = hi, b = hi, c = lo).

Between 1 & 2: Rotating the wheel CW causes:

ontact A to open => Now only B is closed, (pin a = hi, b = hi, c = lo).

Pos. 2: Rotating further CW causes:

C to close => now B and C is closed, This causes a low interrupt on pin b (pin a = hi, b = lo, c
= lo).

New state in SW is set: (pin a = lo, b = hi, c = hi). Now ready for next step.

Between 2 & 3: Rotating further CW causes:

B to open => now only C is closed, (pin a = lo, b = hi, c = hi).

Pos. 3: Rotating further CW causes:

A to close => Now A and C are closed. This causes a low interrupt on pin c (pin a = lo, b = hi,
c = lo).

New state in SW is set: (pin a = hi, b = lo, c = hi). Now ready for next step.

Between 3 & 1: Rotating further CW causes:

contact C to open => Now only A is closed.

Pos.1: This is similar to the first position 1. The pattern is repeated.

This pattern will go on as long as the rotator is turned CW, and the switches open and close
regulairy.

This means:

-In between steps only one switch is closed. This switch stays closed while the 2 other are
changing state.

-Every time a switch closes a low interrupt is generated.

-When going CCW the same pattern will happen, but in opposite order.

-Every time an interrupt is generated a new state has to be set.

-If a false state occurs, initalization routine has to be run until a correct state is reached.