| ??? 10/14/09 16:27 Modified: 10/14/09 16:30 Read: times |
#169702 - 232/1232 Responding to: ???'s previous message |
Joel said:
Ah, I was getting mixed up between the 232 and 1232 for a second, could you confirm this for me a) the max232 is for allowing serial connection, using for example ISP/ICP and b) the max1232 is a supervisor circuit monitoring the supply voltage and managing the reset etc, instead of a hard reset. Yes, the MAX232 is for serial communication. Not all micros do ISP using the serial port, though. The AT89S52 from the example has special ISP lines for this and does not use the serial port. Yes, the MAX1232 is a reset and supply voltage supervisory chip. Joel said:
I have read several threads on various supervisor chips several on 3V3 and 5V applications, and at the end of one someone was talking about designing a more reliable power supply and masterboard. I now cannot find the thread, but can you comment on what makes a setup reliable. What is necessary for example? This was Richard, who has an own theory about this issue. He is thinking that slow supply voltage rises and falls are responsible for flash memory corruption and not the absence of proper reset signal. Nobody else is thinking like him here, to say this very kindly. The use of a proper reset and supply voltage supervisory chip is a must with todays flash code memory micros!!! Some of the micros already contain such a reset circuitry and don't need an external chip. Joel said:
For my project the system may run from the 12 battery, to a 12V-24V DC converter to a regulator for 5V supply to the microcontroller, and 24V supply going to the electronically operated valves which control compressed CO2 flow into a pneumatic actuator. OR the system may run on serial connection of several Ni(Cd/H) batteries. I am unsure of how the supervisor would control the controller in each of these turn on conditions. The controller checks the supply voltage and resets the micro during power ups, power downs and brown-out conditions. For this it is essential to provide a precise and stable 5V supply voltage for the micro and the reset chip. Every standard voltage regulator like the LM7805 or similar can do this. Kai Klaas |
