Analysis of information sources in references of the Wikipedia article "Program counter" in English language version.
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Program Counter (PC) is a register that keeps track of the program sequence, by storing the address of the instruction currently being executed. It is automatically loaded with zero when the chip is powered up or reset. As each instruction is executed, PC is incremented (increased by one) to point to the next instruction.
3.2.12. WRAPMODE […] AS will assume that the processor's program counter does not have the full length of 16 bits given by the architecture, but instead a length that is exactly sufficient to address the internal ROM. For example, in case of the AT90S8515, this means 12 bits, corresponding to 4 Kwords or 8 Kbytes. This assumption allows relative branches from the ROM's beginning to the end and vice versa which would result in an out-of-branch error when using strict arithmetics. Here, they work because the carry bits resulting from the target address computation are discarded. […] In case of the abovementioned AT90S8515, this option is even necessary because it is the only way to perform a direct jump through the complete address space […]
3.2.12. WRAPMODE […] AS will assume that the processor's program counter does not have the full length of 16 bits given by the architecture, but instead a length that is exactly sufficient to address the internal ROM. For example, in case of the AT90S8515, this means 12 bits, corresponding to 4 Kwords or 8 Kbytes. This assumption allows relative branches from the ROM's beginning to the end and vice versa which would result in an out-of-branch error when using strict arithmetics. Here, they work because the carry bits resulting from the target address computation are discarded. […] In case of the abovementioned AT90S8515, this option is even necessary because it is the only way to perform a direct jump through the complete address space […]
