Maxim-integrated MAXQ622 Manual do Utilizador descarregar pdf (Página 63)

MAXQ612/MAXQ622 User’s Guide

Maxim Integrated 4-7

PSF, 08h[04h]

Processor Status Flags Register (8 bits)

Initialization This register is cleared to 80h on all forms of reset.

Access Bit 7 (Z) and bit 6 (S) are read-only.

Bits 4, 3 (GPF1, GPF0), bit 2 (OV), bit 1 (C) and bit 0 (E) are unrestricted read/write.

PSF.0 (E) Equals Flag. This bit flag is set to 1 whenever a compare operation (CMP) returns an

equal result. If a CMP operation returns not equal, this bit is cleared.

PSF.1 (C) Carry Flag. This bit flag is set to 1 whenever an addition or subtraction operation (ADD,

ADDC, SUB, SUBB) returns a carry or borrow.

This bit flag is cleared to 0 whenever an addition or subtraction operation does not return a

carry or borrow.

PSF.2 (OV) Overflow Flag. This flag is set to 1 if there is a carry out of bit 14 but not out of bit 15, or

a carry out of bit 15 but not out of bit 14 from the last arithmetic operation, otherwise, the

OV flag remains as 0. OV indicates a negative number resulted as the sum of two positive

operands, or a positive sum resulted from two negative operands.

PSF.3 (GPF0)

General-Purpose Flag 0

PSF.4 (GPF1) General-Purpose Flag 1. General-purpose flag bits are provided for user software control.

PSF.5 Reserved. Reads return 0.

PSF.6 (S) Sign Flag. This bit flag mirrors the current value of the high bit of the active accumulator

(Acc.15).

PSF.7 (Z) Zero Flag. The value of this bit flag equals 1 whenever the active accumulator is equal to

zero, and it equals 0 otherwise.

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Maxim-integrated MAXQ622 Manual do Utilizador Página 63