SAB80C517A-N18 Siemens Semiconductor Group, SAB80C517A-N18 Datasheet - Page 61

• Manufacturer Part Number: SAB80C517A-N18
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: Siemens Semiconductor Group

Semiconductor Group
Fast internal reset after power-on
The SAB 80C517A can use the oscillator watchdog unit for a fast internal reset procedure after
power-on.
Normally members of the 8051 family (like the SAB 80C517) enter their default reset state not
before the on-chip oscillator starts. The reason is that the external reset signal must be
internally 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 oscillator
watchdog must be enabled. In this case, after power-on the oscillator watch-dog’s RC
oscillator starts working within a very short start-up time (typ. less than 2 micro-seconds). In
the following the watchdog circuitry detects a failure condition for the on-chip oscillator
because this has not yet started (a failure is always recognized if the watchdog’s RC oscillator
runs faster than the on-chip oscillator). As long as this condition is valid the watchdog uses the
RC oscillator output as clock source for the chip rather than the on-chip oscillator’s output.This
allows 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 s
Max.: 34 s
Instruction Set
The SAB 80C517A / 83C517A-5 has the same instruction set as the industry standard 8051
microcontroller.
A pocket guide is available which contains the complete instruction set in functional and
hexadecimal order. Furtheron it provides helpful information about Special Function Registers,
Interrupt Vectors and Assembler Directives.
Literature Information
Title
Microcontroller Family SAB 8051 Pocket Guide
60
Ordering No.
B158-H6497-X-X-7600
SAB 80C517A/83C517A-5
1994-05-01