User Guide

PAMS Technical Documentation 10. Troubleshooting
NSD-5
Issue 1 05/02 Nokia Corporation Page 9
puts 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 squarewave 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 mode, this bus is multiplexed
between sending I and Q data. The signals required to transfer TX data are
CAFE_TX_GATE, CLK9M80, and IQSEL. CAFE_TX_GATE must be high to transfer data, and
the data is clocked by CLK9M80, which is running at 9.8MHz.
MCU
The MCU is used to perform functions that require less processing power than the DSP. It
runs UI software and mode control; interfaces to MBUS; downloads code to flash; reads
and writes the EEPROM; controls charging; and interprets A/D data from CCONT.
Memories
MAD4 interfaces to three memories — Flash, SRAM, and EEPROM. All of them are pow-
ered by 2.8V (Vbb). During Flash programming, Vpp (signal name is Vff_flash on sche-
matic) is driven to Flash memory.