Nutchips behave always as stated by the truth table, except in three special
cases described as follows. Connecting one of the special pins to the negative
supply (GND, at zero volts) we set it to logic zero, thus forcing the Nutchip
to a special state according to the pin used. Leaving the pin disconnected the
Nutchip will not modifiy the Nutchip state. A special input overrides the truth
table. If more than a special input is set to low level at once, the order of
execution is not defined.
The Nutchip is forced to the special state as long as these pins are kept to low level, as shown in this table:
|-ST0||Goes immediately to state zero (st00)||Puts immediately the chip in its initial state, st00. It is very similar to RESET, except that outputs inactive at RESET, whereas setting this pin low drives the output according to the truth table state st00.|
|-HOLD||Temporarly disable the timeout state change||Disables the timeout state switching only, while keeping inputs and remote control active. While state changes in consequence of a timeout are disabled, state changes caused by an input/remote control conditions are still active. The internal timer does not stop ticking, so bringing this pin low and back to high before the timeout expires does not delay the timeout and does not effect the Nutchip behaviour, actually passing unnoticed.|
|-STOP||Stop all state changes, freeze outputs||Freezes the Nutchip as long as the pin stays to logic zero. Disables any state change. The internal timer continues to run, but should the period expire the state will not change. The same applies to the remaining inputs and the remote control action: the Nutchip state does not change as long as this pin is zero.|
How special inputs affect the Nutchip.
The minus sign before pin names reminds that these pins are active when low.
A fourth psecil pin is the -RESET input. This pin, when connected to GND, brings the Nutchip to power-up conditions. Pending timeouts are cleared as long as the -RESET pin remains low. Outputs are in a high-impedance state and the chip restarts from state st00. Any serial communication with the PC is interrupted and must be restarted from the beginning, and any pending remote control reception is lost.