Panasonic KX-TCD705RUM, Service Manual, Page: 25 / 80

6.1. THE BASE BAND SECTION
6.1.1. INTRODUCTION
The base-band section consists of a base-band integrated circuit (BBIC), a Flash PROM, an EEPROM, an LCD Display, a
Microphone, an Earpiece, and power supply/battery management circuits.
6.1.2. THE BASE-BAND INTEGRATED CIRCUIT (BBIC)
The PMB6723 (IC1) is a CMOS device designed to handle all the audio, signal and data processing needed in a DECT handset.
It contains a "burst mode controller" which takes care of DECT specific physical layer and radio section control. It also contains
an ADPCM codec filter used for speech encoding and decoding in the DSP section, a general purpose microcontroller, various
other ADC´s, DAC´s, timers and power control circuitry.
The BBIC interfaces to its external PROM (IC3) via a data/address/control bus. It connects to the EEPROM (IC2) via a serial
interface (SDA and SDC). This serial interface is also used during manufacture and service to connect to an external computer.
6.1.3. FLASH ROM (SEE Fig. 24)
The 1Mbit Flash PROM IC3 contains the operational firmware for the BBIC´s general purpose microprocessor. It is interfaced
to the BBIC using address lines A0 to A17, data lines D0 to D7, and control lines CE (Chip Enable), WE (Write Enable) and OE
(Output Enable).
6.1.4. EEPROM (SEE Fig. 24)
The electrically erasable PROM IC2 is used to store all the temporary operating parameters for the handset (see EEPROM
LAYOUT). It uses a two-line serial data interface with the BBIC, with bi-directional data on IC2 pin5 (TP52), and a 45 kHz clock
on pin6 (TP53).
6.1.5. FACTORY SERIAL PORT (SEE Fig. 24)
In order to communicate with the handset during manufacture and servicing (using a PC) a serial data link has been provided.
Serial data input/output is provided through the I2DAT port (pin 64). The data is clocked through using the I2CLK pin (65). Test
probe pads SDA and SDC are provided for external communications with I2DAT and I2CLK respectively.
To invoke the flash PROM download mode the MODE_SEL test pad must be connected to the 2.65V pad.
A Ground reference Test pad is also provided.
Circuit Diagram
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KX-TCD705RUM / KX-TCD705RUS