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PAMS Technical Documentation
In AMPS mode, the modulated receive RF signals (LIM_P and LIM_N) can be seen coming
into pins 23 and 24 and C216 and C217. For the AMPS Transmit signal, see AMPSMOD
above.
Both the TX and RX paths are also described in section Audio Failures.
MAD4
The MAD4 ASIC is the core of the baseband functionality and basically contains the DSP,
MCU, and CDMA logic. The DSP is used to perform functions such as RF control, DTMF
tone generation, and it implements the vocoder. The MCU is used to perform functions
that do not require as much power. These are higher level functions such as UI software
(key presses, backlighting, LCD functions, etc.) and mode control.
DSP
The DSP sends control signals to the RF via PDMs. In order to control RF parameters such
as TX_VCO_CAL or TX_LIM_ADJUST, a continuously variable analog signal must be used.
Since the DSP outputs only digital signals, a PDM RC circuit is used to convert the digital
output signal to an average analog voltage. A PDM line will always have a series resistor
followed by a shunt capacitor. The output of the MAD4 PDM lines will appear as square-
wave signals. However, after the shunt capacitor the signals will appear to be DC with
perhaps a slight ripple. The RC circuit acts as an integrator in order to yield the average
value (DC) of the squarewave signal.
The transmit data bus (TXD(7:0)) is 8 bits wide. In CDMA this bus is multiplexed between
sending I and Q data. The signals required to transfer TX data are TXGATE, CLK9M80, and
IQSEL. TXGATE must be high to transfer data, and the data is clocked by CLK9M80, which
is running at 9.8MHz. In AMPS mode, CLK9M80 is running at 120kHz, therefore, data is
being transferred from MAD4 to CAFE at 120kHz.
The JTAG lines are intended to be used to operate the DSP (and/or MCU) externally.
External Regulator
A separate 2.8V external regulator powers the Lead (DSP) independently. Eventually, the
next version of MAD4 will be used and the Lead may be powered by VMAD from CCONT.
See External Regulators section under CCONT/Linear Regulators. Note: This regulator is
also mentioned in section Power Circuitry.
Note: this regulator may not be present on any HW that uses MAD4_V3.
MCU
The MCU is used to perform functions that require less processing power than the DSP. It
runs UI software, mode control, interfaces to MBUS, downloads code to flash, reads and
writes the EEPROM, controls charging, and interprets A/D data from CCONT. (Used only
in NSD–3AW [and NDS–1AW] NBA chip is used in synchronization between MAD4 and
SRAM.)
Issue 1 04/01
Disassembly/Troubleshooting Instructions
Nokia Mobile Phones Ltd.
NSD-6
Page 13
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Troubleshooting
