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Reading Atmel 24C24N in circuit
Posted by:
Arik Funke
()
Date: March 15, 2012 03:21PM
Hi,
I am trying to read out an powered down Atmel 24C02N in a live circuit. (Connected to a battery monitoring IC.) Unfortunately Ponyprog only shows the message "Device not responding".
The eeprom in the circuit is normally powered down and only energised should the IC have lost power and need to read the battery settings. The IC is always energised as it is connected directly to the battery which it is monitoring.
Given that the eeprom is normally unpowered, I though it was sufficiently "decoupled" to allow me to read it in its circuit. I thus energised the eeprom with an external 5V power supply and built the following interface (derived fom SiProg.)
RS232 24C02N
5 -------------------------- GND
7 ---X----- 4K7 ------------ SCL
4 ------Y-- 4K7 ---o-------- SDA
8 -----------------|
Where X & Y are connected via 5.1V Zener diodes to GND. A0, A1, A2, WP and GND of the EEPROM are all connected to RS-232 pin 5 as well as the negativ terminal of the external power supply.
One observation I made was that when 5V and GND are connected to the EEPROM (SDA & SCL left only connected to the circuit on which they sit), SCK and SDA are high. Should this be the case or is this an interaction with the mictroprocessor?
Many thanks.
Arik
I am trying to read out an powered down Atmel 24C02N in a live circuit. (Connected to a battery monitoring IC.) Unfortunately Ponyprog only shows the message "Device not responding".
The eeprom in the circuit is normally powered down and only energised should the IC have lost power and need to read the battery settings. The IC is always energised as it is connected directly to the battery which it is monitoring.
Given that the eeprom is normally unpowered, I though it was sufficiently "decoupled" to allow me to read it in its circuit. I thus energised the eeprom with an external 5V power supply and built the following interface (derived fom SiProg.)
RS232 24C02N
5 -------------------------- GND
7 ---X----- 4K7 ------------ SCL
4 ------Y-- 4K7 ---o-------- SDA
8 -----------------|
Where X & Y are connected via 5.1V Zener diodes to GND. A0, A1, A2, WP and GND of the EEPROM are all connected to RS-232 pin 5 as well as the negativ terminal of the external power supply.
One observation I made was that when 5V and GND are connected to the EEPROM (SDA & SCL left only connected to the circuit on which they sit), SCK and SDA are high. Should this be the case or is this an interaction with the mictroprocessor?
Many thanks.
Arik