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Intel 8085
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===Programming model=== {| class="infobox" style="font-size:88%;width:34em;" |- |+ Intel 8085 registers |- | {| style="font-size:88%;" |- | style="width:10px; text-align:center;"| <sup>1</sup><sub>5</sub> | style="width:10px; text-align:center;"| <sup>1</sup><sub>4</sub> | style="width:10px; text-align:center;"| <sup>1</sup><sub>3</sub> | style="width:10px; text-align:center;"| <sup>1</sup><sub>2</sub> | style="width:10px; text-align:center;"| <sup>1</sup><sub>1</sub> | style="width:10px; text-align:center;"| <sup>1</sup><sub>0</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>9</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>8</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>7</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>6</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>5</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>4</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>3</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>2</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>1</sub> | style="width:10px; text-align:center;"| <sup>0</sup><sub>0</sub> | style="width:auto;" | ''(bit position)'' |- |colspan="17" | '''Main registers''' |- style="background:silver;color:black" | style="text-align:center;" colspan="8"| A | style="text-align:center;background:#DDD" colspan="8"| [[Flag (computing)|Flags]] | style="width:auto; background:white; color:black;"| '''P'''rogram '''S'''tatus '''W'''ord |- style="background:silver;color:black" | style="text-align:center;" colspan="8"| B | style="text-align:center;" colspan="8"| C | style="background:white; color:black;"| '''B''' |- style="background:silver;color:black" | style="text-align:center;" colspan="8"| D | style="text-align:center;" colspan="8"| E | style="background:white; color:black;"| '''D''' |- style="background:silver;color:black" | style="text-align:center;" colspan="8"| H | style="text-align:center;" colspan="8"| L | style="background:white; color:black;"| '''H''' (indirect address) |- |colspan="17" | '''[[Index registers]]''' |- style="background:silver;color:black" | style="text-align:center;" colspan="16"| SP | style="background:white; color:black;"| '''S'''tack '''P'''ointer |- |colspan="17" | '''[[Program counter]]''' |- style="background:silver;color:black" | style="text-align:center;" colspan="16"| PC | style="background:white; color:black;"| '''P'''rogram '''C'''ounter |- |colspan="17" | '''[[Status register]]''' |- style="background:silver;color:black" | style="text-align:center; background:white" colspan="8" | | style="text-align:center;"| [[Sign flag|S]] | style="text-align:center;"| [[Zero flag|Z]] | style="text-align:center;"| - | style="text-align:center;"| [[Half-carry flag|AC]] | style="text-align:center;"| - | style="text-align:center;"| [[Parity flag|P]] | style="text-align:center;"| - | style="text-align:center;"| [[Carry flag|CY]] | style="background:white; color:black" | Flags |} |} The processor has seven 8-bit [[processor register|registers]] accessible to the programmer, named A, B, C, D, E, H, and L, where A is also known as the accumulator. The other six registers can be used as independent byte-registers or as three 16-bit register pairs, BC, DE, and HL (or B, D, H, as referred to in Intel documents), depending on the particular instruction. Some instructions use HL as a (limited) 16-bit accumulator. As in the 8080, the contents of the memory address pointed to by HL can be accessed as pseudo register M. It also has a 16-bit [[program counter]] and a 16-bit [[Stack-based memory allocation|stack pointer]] to memory (replacing the 8008's internal [[stack (data structure)|stack]]). Instructions such as PUSH PSW, POP PSW affect the Program Status Word (accumulator and flags). The accumulator stores the results of arithmetic and logical operations, and the flags register bits (sign, zero, auxiliary carry, parity, and carry flags) are set or cleared according to the results of these operations. The sign flag is set if the result has a negative sign (i.e. it is set if bit 7 of the accumulator is set). The auxiliary or half carry flag is set if a carryover from bit 3 to bit 4 occurred. The parity flag is set to 1 if the parity (number of 1-bits) of the accumulator is even; if odd, it is cleared. The zero flag is set if the result of the operation was 0. Lastly, the carry flag is set if a carryover from bit 7 of the accumulator (the MSB) occurred.
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