Nokia RH-41 Series Technical Documentation Manual page 20

RH-41
System Module
HEADINT
An accessory is detected by the HeadInt- line, which is connected to the XEARP inside
the system connector. When an accessory is connected, it disconnects XEARP from
HEADINT, and the UEM detects it and generates an interrupt (UEMINT) to the MCU. After
that, the HOOKINT line is used to determine which accessory is connected. This is done
by the voltage divider, which consists of the phone's internal pull-up and accessory-spe-
cific pull-down. The voltage generated by this divider is then read by the ad- converter of
UEM. The HOOKINT- interrupt is generated by the button in the headset or by the acces-
sory external audio input.
2.7V
Hookint
/MBUS
EAD
Headint Headint
MIC1Bias
MIC1P
MIC1N
HF
3...25k
HFCM
UEM
Page 20
MIC
Figure 6: System Connector
2k2
2.1V
33n
33n
0.8V
100p
Figure 7: Accessory Detection / External Audio
Nokia Corporation
CCS Technical Documentation
GND
VIN
PWMO
XMICP
XMICN
HF
HFC
MICN
1.8V
0.3V
Confidential
MicGND
Issue 2 09/2003