– 5–12 –
The GSM Standard requires that the receiver audio frequency response must fit within the mask shown below.
Figure 5.12. Handheld GSM Receive Audio Frequency Response
The phone is designed to meet requirements with a Type 1 artificial ear.
1
2
3
4
+1 db
-2 db
-5 db
-5 db
0 db
0 db
0 db
-6 db
+3 db
-0 db
-3 db
-9 db
A second speaker is mounted in the rear case for DTHF operation.
Ring tones and melodies are played via the loud speaker. The volume level of ring tones is defined
by the 6-bit PWM register setting in AD6521, and melody tone volume defined by the
MASOUND_DEVICECONTROL register setting in the YMU762.
Timer 1 in AD6521 is used to time the period between switching the ringing on and off to make the
tone. For complex ringing tones, the buzzer volume can be altered after each time-out of Timer 1.
There is a watchdog timer and three 16 bit general-purpose timers which can be used either as
auto reload or one-shot timers to provide interrupts to the ARM CPU. A pre-scaler and 16-bit
register defines the timer clock duration. The watchdog timer receives a 217 Hz clock signal from
clock module. The time-out is fixed at 1024 clock ticks, which gives a time-out of approximately
4.72s. The general-purpose timers can receive different clock sources. The clock sources can be
System clock, MicroSM Clock, MicroSM timetick, 32KHz oscillator.
$8014:0000 Watchdog_R
Watchdog register,
0 bit
Write only, reserved
$8014:0002 Watchdog_CR
Watchdog control register
1 bit
Read/Write
$8014:0004 Watchdog_INT
Watchdog interrupt register
1 bit
Read/Write
$8020:0080 TimerStatus
6 bits
Read/Write
$8020:0082 Reserved
0 bit
Read/Write
$8020:0084 EndCountA
16 bits
Read/Write
$8020:0086 TimerAControl
12 bits
Read/Write
$8020:0088 EndCountB
16 bits
Read/Write
$8020:008A TimerBControl
12 bits
Read/Write
$8020:008C EndCountC
16 bits
Read/Write
$8020:008E TimerCControl
12 bits
Read/Wr
5.3.3. Receiver
5.4. Timers
5.3.4. Loud Speaker
Volume Level
PGA
Volume
Total Gain
