An external RESET signal of three clock period duration (minimum) restores the processor's internal program counter to zero. Program execution thus begins with memory location zero, following a RESET. Systems which require the processor to wait for an explicit startup signal will store a halt instruction (EI,HLT) in the first two locations. A manual or an automatic INTERRUPT will be used for starting. In other systems, the processor may begin executing its stored program immediately. Note, however, that the RESET has no effect on status flags, or on any of the processor's working registers (accumulator, registers, or stack pointer). The contents of these registers remain indeterminate, until initialized explicitly by the program.
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