High-Performance SAB 80C517A/83C517A-5 8-Bit CMOS Single ...

SAB 80C517A/83C517A-5Fast internal reset after power-onThe SAB 80C517A can use the oscillator watchdog unit for a fast internal reset procedure afterpower-on.Normally members of the 8051 family (like the SAB 80C517) enter their default reset state notbefore the on-chip oscillator starts. The reason is that the external reset signal must beinternally synchronized and processed in order to bring the device into the correct reset state.Especially if a crystal is used the start up time of the oscillator is relatively long (typ. 1 ms).During this time period the pins have an undefined state which could have severe effects e.g.to actuators connected to port pins.In the SAB 80C517A the oscillator watchdog unit avoids this situation. However, the oscillatorwatchdog must be enabled. In this case, after power-on the oscillator watch-dog’s RCoscillator starts working within a very short start-up time (typ. less than 2 micro-seconds). Inthe following the watchdog circuitry detects a failure condition for the on-chip oscillatorbecause this has not yet started (a failure is always recognized if the watchdog’s RC oscillatorruns faster than the on-chip oscillator). As long as this condition is valid the watchdog uses theRC oscillator output as clock source for the chip rather than the on-chip oscillator’s output.Thisallows correct resetting of the part and brings also all ports to the defined state.Delay time between power-on and correct reset state:Typ.: 18 µsMax.: 34 µsInstruction SetThe SAB 80C517A / 83C517A-5 has the same instruction set as the industry standard 8051microcontroller.A pocket guide is available which contains the complete instruction set in functional andhexadecimal order. Furtheron it provides helpful information about Special Function Registers,Interrupt Vectors and Assembler Directives.Literature InformationTitleMicrocontroller Family SAB 8051 Pocket GuideOrdering No.B158-H6497-X-X-7600Semiconductor Group 61