SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 38

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

System Reset
6.2
Reset Output Pin (RO)
As mentioned before the SAB 80C517 internally synchronizes an external reset signal at pin
RESET in order to perform a reset procedure. Additionally, the SAB 80C517 provides several "fail-
save" mechanisms, e.g. watchdog timer and oscillator watchdog, which can internally generate a
reset, too. Thus, it is often important to inform also the peripherals external to the chip that a reset
is being performed and that the controller will soon start its program again.
For that purpose, the SAB 80C517 has a pin dedicated to output the internal reset request. This
reset output (RO) at pin 82 shows the internal (and already synchronized) reset signal requested
by any of the three possible sources in the SAB 80C517: external hardware reset, watchdog timer
reset, oscillator watchdog reset. The duration of the active low signal of the reset output depends
on the source which requests it. In the case of the external hardware reset it is the synchronized
external reset signal at pin RESET. In the case of a watchdog timer reset or oscillator watchdog
reset the RESET OUT signal takes at least two machine cycles, which is the minimal duration for a
reset request allowed. For details - how the reset requests are OR-ed together and how long they
last - see also chapter 7.8 "Fail-Save Mechanisms".
Semiconductor Group
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