Dsp Main Features - Nokia NSW-5 Series Service Manual

PAMS Technical Documentation
– battery and charging monitoring
MCU reads the battery type (BTYPE), temperature (BTEMP) and voltage
(VBAT) values by AD–converter in CCONT, and phone's operation is al-
lowed only if the values are reasonable. Charging current is controlled by
writing suitable values to PWM control in CCONT.
MCU reads also charger voltage (VCHAR) and charging current values
(IBAT).
– production/after sales tests and tuning
Flash and EEPROM loading, baseband tests, RF tuning
– Control of CCONT via serial bus
MCU writes controls (regulators on/off, Watchdog reset, charge
PWM control) and reads AD–conversion values.
For AD–conversions MCU gives the clock for CCONT (bus clock),
because the only clock in CCONT is sleep clock, which has too low fre-
quency.

DSP main features

The DSP (Digital Signal Processor) is in charge of the channel and
speech coding according to the IS–136 specification. The block consists
of a DSP and internal ROM and RAM memory. The input clock is 9.72
MHz, and DSP has an own internal PLL–multiplier. Main interfaces are to
MCU, and via System Logic to COBBA and RF.
– Analog transmit
Audio signal in analog mode is fed to the COBBA codec, where it is
routed, amplified and converted by internal A/D converter into bitstream
(the sample rate is in digital mode 8.0 kHz and in analog mode 8.1 kHz).
The digitized speech is processed by the DSP audio modules into 48.6
kHz audio. This audio is FM modulated into I/Q samples at 97.2 kHz. The
samples are sent via System Logic transmit buffer to the COBBA TXI/Q
D/A converters. This I/Q modulated analog signal goes then to RF unit
I/Q inputs. DSP must also perform echo cancelling in HF mode.
– Analog receive
In analog receive the signal is demodulated by DEMO (block in COBBA)
and the sample rate is 48.6 kHz. The samples are directed trough Sys-
tem Logic to DSP. DSP performs audio processing and finally transfers
the digital audio (8.1 kHz sample rate) back to COBBA, where they are
D/A converted. Resulting audio signal is routed and amplified to the ear-
piece or external loudspeaker.
– Digital transmit
In digital transmit mode DSP processes speech data in 20 ms slots. It
performs speech encoding (EFR), CRC generation, convolutional coding
and interleaving. Finally it sends the symbols to the System Logic modu-
lator. The modulator performs the π/4 DQPSK modulation. System Logic
Issue 1 10/00
E Nokia Mobile Phones Ltd.
NSW-5
System Module UT5U
Page 25