HD643303x Hitachi, HD643303x Datasheet - Page 37

• Manufacturer Part Number: HD643303x
• Description: Hitachi Microcomputer
• Manufacturer: Hitachi

Bit 5—Half-Carry Flag (H): When the ADD.B, ADDX.B, SUB.B, SUBX.B, CMP.B, or NEG.B
instruction is executed, this flag is set to 1 if there is a carry or borrow at bit 3, and cleared to 0
otherwise. When the ADD.W, SUB.W, CMP.W, or NEG.W instruction is executed, the H flag is
set to 1 if there is a carry or borrow at bit 11, and cleared to 0 otherwise. When the ADD.L,
SUB.L, CMP.L, or NEG.L instruction is executed, the H flag is set to 1 if there is a carry or
borrow at bit 27, and cleared to 0 otherwise.
Bit 4—User Bit (U): Can be written and read by software using the LDC, STC, ANDC, ORC,
and XORC instructions.
Bit 3—Negative Flag (N): Indicates the most significant bit (sign bit) of data.
Bit 2—Zero Flag (Z): Set to 1 to indicate zero data, and cleared to 0 to indicate non-zero data.
Bit 1—Overflow Flag (V): Set to 1 when an arithmetic overflow occurs, and cleared to 0 at other
times.
Bit 0—Carry Flag (C): Set to 1 when a carry occurs, and cleared to 0 otherwise. Used by:
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The carry flag is also used as a bit accumulator by bit manipulation instructions.
Some instructions leave flag bits unchanged. Operations can be performed on CCR by the LDC,
STC, ANDC, ORC, and XORC instructions. The N, Z, V, and C flags are used by conditional
branch (Bcc) instructions.
For the action of each instruction on the flag bits, see appendix A.1, Instruction List. For the I and
UI bits, see section 5, Interrupt Controller.
2.4.4 Initial CPU Register Values
In reset exception handling, PC is initialized to a value loaded from the vector table, and the I bit
in CCR is set to 1. The other CCR bits and the general registers are not initialized. In particular,
the stack pointer (ER7) is not initialized. The stack pointer must therefore be initialized by an
MOV.L instruction executed immediately after a reset.
Add instructions, to indicate a carry
Subtract instructions, to indicate a borrow
Shift and rotate instructions, to store the value shifted out of the end bit
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