User's Manual

REPORT NO : HCT-F02-1104 FCC ID : N5ZDN308 DATE : NOVEMBER 12, 2002
HYUNDAI CALIBRATION & CERTIFICATION TECHNOLOGIES CO., LTD.
SAN 136-1, AMI-RI , BUBAL-EUP, ICHEON-SI,KYOUNKI-DO, 467-701,KOREA
TEL : [phone] FAX : [phone]
4. Circuit Description
DN308 unit consists of three circuit boards; Main board, and Key board. The Main board is the
core of the unit whereas other boards are simple,1that is, the Key board has only contact switches.
4-1. Main Board
Main Board circuit can be divided into several blocks, which are CPU block to control the whole
system, DSP block to manipulate the audio signal, and analog block to control the input/output
audio signal, and power amplifier.
4-1-1. CPU block
Microprocessor(IC1) is powered by 3V DC/DC converter and controls the power of the DSP and
Memory to save the batteries. It controls the LCD and check whether a key is pressed. Every time
the CPU detects an event like key-in, it updates the contents of LCD and control the peripherals as
the action of event which can be recording or playing back, etc. Mainly the important
processes are to control DSP and Memory.
Every Input from the Key board is connected to an input port of the CPU and it can be checked and
activated by its falling edge.
4-1-2. DSP(Digital Signal Processor) block
DSP Chip D6571E receives the digitized analog signal from the audio CODEC and compress it to
reduce the data size when recording. After compressing, the CPU gets the compressed data from
DSP and save it to the Memory. On the opposite way, DSP gets the compressed data from CPU, of
course CPU reads the data from the memory, and then decompress the data and send it to the audio
CODEC for D/A conversion while playing back.
There is a simple command protocol between the CPU and the DSP to communicate each other.
Every time the CPU sends command and then waits the response from the DSP. If there is no
response, the CPU cannot proceed the action and writes D-err on LCD.