User Guide

PAMS
Technical Documentation
NSE–8/9
System Module
Page 2– 72
Issue 1 07/99
– GenSIO_0: Serial data clock, 1.083 MHz from MAD2PR1 (GenSClk)
– GenSIO_1: Serial Data from MAD2PR1 (GenSDIO),
Data is read on the rising edge of the clock. On every eight clock pulse,
the data is transferred from the shift register and processed as 8–bit
parallel data. LCDCD is read on the rising edge of every eight clock
signal.
Keyboard
Keypad switch matrix
The keypad consists of a matrix of 16 switches, (0 – 9, #, *, Clear,
Previous (B), NEXT (Y) and SOFT–A (Navi–key) ). These are the
references on the schematics. Bold indicates the keyboard functionality,
which is determined by software.
The keypad keys are connected in a 4 by 4 matrix. The 4 columns
(outputs) are normally held logic low by the MAD2PR1. The 4 rows
(inputs) are connected to the MAD2PR1 – when any of these inputs goes
low (there are pull–ups inside the MAD2PR1) the MAD2PR1 interrupts the
MCU, which then commences scanning. This involves taking all the
columns high then taking each individual column low in turn. When a low
is received on a row input, it can be deduced, which key is pressed from
the row input number and the column output, which is currently low.
Table 36. Keyboard matrix signal levels
Name Property Min Typ Max Unit Notes
COL (3:0)
VoL 0 Logic Low 0.5 V
Keyboard
matrix col
VoH 2.1 Logic High Vbb V
matrix
col
-
umns
ROW (4:1)
ViL 0 Logic Low 0.6 V
Keyboard
ti
ViH 2.0 Logic High Vbb V
matrix rows
The keypad consists of gold flashed PCB tracks above which are placed
metal keydomes.
The ROW inputs on the MAD are protected against ESD by V301 since
rows are the outer ring of the pcb pads.
The power key, S416, is connected through R413 to the CCONT via the
line ’PWRON’ and to ’ROW0’ trough the diode V410 and R423. When
activated both lines are pulled low.
When the key is pressed, row0 will go low, but the value of row0 will not
be changed when the column outputs are set high at the start of the
scanning process. This fact uniquely identifies the key. A diode is
necessary to protect the MAD2PR1 against the pull up of ”PWRON” to
Vdc_out inside CCONT.
R423 is used for ESD suppression of discharges on the power on key,
before reaching the MAD input.