The EEPROM of a Philips DC 5xx carradio

 - disper
 - tirp
 - DC5xx radio *

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A friend of mine bought a car in 2001. There was a Philips DC501 carradio inside, but he forgot to ask the security code. Thus the carradio was pratically unusable. But we saw the radio pcb contains a 24C02 IIC EEPROM, so the least we could do is having a look at it's contents...

I'm not going to explain here in detail how to circumvent the security code of the radio. If you are able to read and write the non-volatile memory, finding the information on this page is only a matter of time.

The 24C02 is a IIC serial EEPROM with 2k of memory (datasheet). This memory is used to store channel frequencies, the security code and status and some other things. You can find below what I've found out.

Channel presets

There is space for 5 bands in the memory area 0x00-0x4f (band 0 starts on 0x00, band 1 on 0x10, etc.). My radio only had 3 FM bands, other models probabely also have two AM bands. Each band can use 16 bytes of memory (see table). The currently selected band can be found in the high nibble of byte 0x72. A 16-byte band memory block is used as follows:

Byte offsetFunction
0x00-0x01 Frequency preset 1
0x02-0x03 Frequency preset 2
0x04-0x05 Frequency preset 3
0x06-0x07 Frequency preset 4
0x08-0x09 Frequency preset 5
0x0a-0x0b Frequency preset 6
0x0c-0x0d Current frequency for manual tuning
0x0e-0x0f Unused (0xffff by default)

I don't know the relation between the 16-bit number of the frequency and the frequency in Hz.


Byte# Bit# Function
0x59 4-7 =1: display shows 'Cod <>', code cannot be entered until some time has passed.
=2: display shows 'Cod', code can be entered.
0x59 0-3 First digit of security code
0x5a 4-7 Second digit of security code
0x5a 0-3 Time to wait before code can be entered (when display shows 'Cod <>'). 0x0f=1min, 0x0E=2min, 0x0D=4min, ....
0x5b 4-7 =1: Radio is locked, code has te be entered
=2: Radio is unlocked, no code has to be entered.
0x5b 0-3 Third digit of security code
0x5c 4-7 Fourth digit of security code

Current radio settings

Byte# Bit# Function
0x72 4-7 Radio band (0=FM1, 3=FM2, 4=FM3)
0x78 4-7 Selected preset channel for band 0
0x78 0-4 =0x0d: Preset selected, =0x04: manual tuning [band 0]
0x7b 4-7 Selected preset channel for band 3
0x78 0-4 =0x0d: Preset selected, =0x04: manual tuning [band 3]
0x7c 4-7 Selected preset channel for band 4
0x78 0-4 =0x0d: Preset selected, =0x04: manual tuning [band 4]