Product: AnswerMan


NAME: Analog Threshold Limits


Date: 05/05/00


Introduction: This application note shows how to use the analog threshold limits to monitor a voltage with the use of only the AnwserMan.




Background: AnwserMan may be set up to automatically monitor any if the analog inputs and set corresponding digital outputs when a high or a low limit has been exceeded. With this feature the AnwserMan can exercise autonomy by not requiring the services of a central computer to react to local conditions.




How it works: To use the analog threshold limits the SL or the SLD commands are used to monitor voltages on the AnwserMan’s analog inputs. The uses of these commands are explained in detail in the AnwserMan datasheet. The commands allow the user to set a minimum and a maximum voltage for the AnwserMan to monitor. The SL command stores these voltages in RAM where as the SLD command stores the voltages in the EEPROM. When enabled the AnwserMan will set an output bit high if the voltage being monitored is not within specified limits. The output bit will stay in the high state until the voltage returns to specified range. The output bit is predetermined when the analog input channel is selected. When configuring the AnwserMan be sure to set both bit seven (twelve for 12-bit limit checking) and bit two, otherwise the limit checking will not work. The analog limit checking function can be used with either the 8-bit channels of the AnwserMan Jr. & Sr., or with the 12-bit channels of the AnwserMan Sr..