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    Description:

    This instruction performs a compare between register Rd and a constant. The register is not changed. All conditional branches can be used after this instruction.

    Operation:

    Rd - K

    Syntax: Operands: Program Counter:

    CPI Rd,K 16 ≤ d ≤ 31, 0≤ K ≤ 255 PC ← PC + 1

    16-bit Opcode:

    0011

    KKKK

    dddd

    KKKK

    Status Register (SREG) and Boolean Formula:

    I

    T

    H

    S

    V

    N

    Z

    C

    -

    -

    ⇔

    ⇔

    ⇔

    ⇔

    ⇔

    ⇔

    H: Rd3 ¯ • K3 + K3 • R3 + R3 • Rd3 ¯ Set if there was a borrow from bit 3; cleared otherwise

    S: N ⊕ V, For signed tests.

    V: Rd7 Rd7 • K7 ¯ • R7 ¯ + Rd7 ¯ • K7 • R7 Set if two's complement overflow resulted from the operation; cleared otherwise.

    N:R7 Set if MSB of the result is set; cleared otherwise.

    Z: R7 ¯ • R6 ¯ • R5 ¯ • R4 ¯ • R3 ¯ • R2 ¯ • R1 ¯ • R0 ¯ Set if the result is $00; cleared otherwise.

    C: Rd7 ¯ • K7 + K7 • R7 + R7 • Rd7 ¯ Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.

    R (Result) after the operation.

    Example: 

    cpi r19,3 ; Compare r19 with 3
brne error ; Branch if r19⇔3
...
error: nop ; Branch destination (do nothing)

    Words: 1 (2 bytes)

    Cycles: 1

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