Maxim-integrated MAX31782 Manual do Utilizador descarregar pdf (Página 176)

Maxim Integrated 19-11

MAX31782 User’s Guide

Revision 0; 8/11

19.6.5 Overflow Flag

The Overflow flag (PSF.2) is a static flag indicating that the carry or borrow bit (Carry status Flag) resulting from the last

ADD/ADDC or SUB/SUBB operation but did not match the carry or borrow of the high order bit of the active accumula-

tor. The overflow flag is useful when performing signed arithmetic operations.

The following instructions can alter the Overflow flag:

• ADD src (Add source to active accumulator)

• ADDC src (Add source and Carry to active accumulator)

• SUB src (Subtract source from active accumulator)

• SUBB src (Subtract source and Carry from active accumulator)

19.7 Controlling Program Flow

The MAX31782 provides several options to control program flow and branching. Jumps may be unconditional, con-

ditional, relative, or absolute. Subroutine calls store the return address on the hardware stack for later return. Built-in

counters and address registers are provided to control looping operations.

19.7.1 Obtaining the Next Execution Address

The address of the next instruction to be executed can be read at any time by reading the Instruction Pointer (IP)

register. This can be particularly useful for initializing loops. Note that the value returned is actually the address of the

current instruction plus 1, so this will be the address of the next instruction executed as long as the current instruction

does not cause a jump.

19.7.2 Unconditional Jumps

An unconditional jump can be relative (IP +127/-128 words) or absolute (to anywhere in program space). Relative

jumps must use an

8-bit immediate operand, such as

Label1:   ;mustbewithin+127/-128wordsoftheJUMP

...

jump Label1

Absolute jumps can use a 16-bit immediate operand, a 16-bit register, or an 8-bit register.

jump LongJump ;assemblesto: movePFX[0],#high(LongJump)

    ;   jump  #low(LongJump)

jump DP[0]  ;absolutejumptotheaddressinDP[0]

If an 8-bit register is used as the jump destination, the prefix value is used as the high byte of the address and the

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Maxim-integrated MAX31782 Manual do Utilizador Página 176