Aci; External Audio; External Microphone Connection - Nokia NSB-9 Service Manual

NSB-9
System Module and User Interface

ACI

(Accessory Control Interface) is a point-to-point, bi-directional serial bus. ACI has three
main features:
• Insertion and removal detection of an accessory device
• Identify and authenticate the connected accessory
• Data bus for accessory control
The accessories are detected by the HEADINT signal when the accessory is inserted.
Normally when no accessory is present, the 100k pull-up resistor pulls up the HEADINT
signal to VFLASH1. When the accessory is inserted, the external "insertion and removal"
resistor works as a voltage devider and decreases the voltage level below the threshold
Vhead. Thereby the comparator output will be changed to high state causing an inter-
rupt.
When the accessory is removed, the voltage level of HEADINT increases again to
VFLASH1. This voltage level is higher than the threshold of the comparator and thereby
its output will be changed to low state. This change causes an interrupt.
Those HEADINT interrupts are initiated by the accessory detection or removal sequence.

External Audio

NSB-9 is designed to support fully differential external audio accessory connection by
using Pop-Port system connector. Pop-Port connector has serial data bus called ACI
(Accessory Control Interface) for accessory insertion and removal detection, utilizing,
identification and authentication. ACI line is also used for accessory control purposes.
Audio support with Pop-Port system connector:
• 2-wire differential mic input
• 4-wire fully differential stereo audio output (used also as an FM-radio antenna)

External Microphone Connection

The external microphone input is fully differential and lines are connected to the UEM
microphone input MIC2P/N.
The UEM (MICB2) provides bias voltage. Microphone input lines are ESD protected. Cre-
ating a short circuit between the headset microphone signals (with headset button) gen-
erates the hook signal. When the accessory is not connected, the UEM resistor pulls up
the HookInt signal. When the accessory is inserted and the microphone path is biased the
HookInt signal decreases to 1.8V due to the microphone bias current flowing through the
resistor. When the button is pressed the microphone signals are connected together, and
the HookInt input will get half of micbias dc value 1.1 V. This change in DC level will
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Nokia Corporation
CCS Technical Documentation
Issue 1 04/03