Cbus Interface; Fbus; Eci Interface; Charger Interface - Nokia n81 Service Manual

CBUS interface

CBUS is a "main" system control bus in BB5. RAPIDO controls the functionality of EM ASIC (N2200) and EM ASIC
(N2300) ASICs with CBUS.
CBUS is a four-wire half-duplex master-slave interface. In BB5 CBUS clock frequency is 2.4 MHz.

FBUS

USB and FBUS have multiplexed interface between EM ASIC (2300) and RAPIDO.

ECI interface

The ECI (Enhancement Control Interface) is a point-to-point, bi-directional, single line serial bus.
The purpose of the ECI is to identify and authenticate the accessory, and to act as a data bus (intended for
control purposes) between the phone and the accessory .

Charger interface

Charging control and charge switch are situated in EM ASIC (N2300).
If the temperature rises too high and the thermal protection is activated, EM ASIC (N2300) goes to protection
mode.

SIM interface

The device has one SIM (Subscriber Identification Module) interface. It is only accessible if battery is removed.
The SIM interface consists of an internal interface between RAPIDO and EM ASIC (N2200), and of an external
interface between N2200 and SIM contacts.
The SIM IF is shown in the following figure:
The EM ASIC handles the detection of the SIM card. The detection method is based in the BSI line. Because of
the location of the SIM card, removing the battery causes a quick power down of the SIM IF.
Page 6 –18
Figure 58 SIM interface
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System Module and User Interface
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