The issue of circuit loading is addressed by incorporating push-pull pin driver circuitry in the programming instrument and adapters. Also, in some cases, the collision can cause data corruption within the eeprom itself as the chip is trying to process and respond to commands from two different sources (processor and programmer). The resulting data collision causes invalid or incorrect data to be read by the programming instrument. When this happens the processor (microcontroller) will begin communicating with the eeprom at the same time the programming instrument is attempting to read data from the chip. If the power (voltage) applied to the eeprom chip is the same level as the standard assembly operating voltage, then the entire module will power up and become active (see photo right). The backfeed occurs because the power pins on the chip to which the programming unit is connected are also connected to the common power bus which feeds the entire module circuit assembly. The second condition which affects successful in-circuit programming is caused by power backfeeding into the circuit assembly. The programming instrument must have sufficient drive capability to overcome the load presented by the existing module circuitry (yellow traces) to allow the application of valid logic levels. If the part does not see a valid logic level on all pins necessary for communication then the part will not respond.
A logic level is the voltage necessary for the part to interpret the applied signal as a logic 0 (low) or logic 1 (high). Second, each pin on the part which is required for successful communication must be driven to a valid logic level while the part is being read. First the part must have power applied in order to operate. When the programming instrument is attached to the part and instructed to read the data two fundamental conditions must occur. The hi-lited (yellow) circuit traces show how the part is connected to other components on the assembly.
8 pin eeprom programmer serial#
The part shown in the photo on the right is a 95320 serial eeprom. These are existing circuit loading and existing circuit activity. OBSTACLES TO SUCCESS - There are two primary obstacles or conditions which can interfere with successful in-circuit eeprom work. Andromeda Research is know for providing an excellent in-circuit reading and programming solution for applications where unsoldering the part from the circuit assembly is not the desired approach. The AR-32A programming instrument, when used with adapters specifically designed for in-circuit work, provides the best opportunity for successful part communication without removal from the assembly. In other words make a part which is already connected to other components look like it is not.Īndromeda Research products are designed to work with eeproms and microcontrollers in-circuit. The challenge is to make the part appear to the programming instrument as though it is an unconnected device. In-circuit access to an 8 pin serial eeprom or microcontroller poses a challenge to product designers as the part is not only soldered to the circuit assembly but is also connected to existing components on the assembly itself. THE CHALLENGES OF IN-CIRCUIT READING AND PROGRAMMING