Datasheet

Section 2 CPU
Rev.7.00 Mar. 18, 2009 page 47 of 1136
REJ09B0109-0700
Bit Bit Name Initial Value R/W Description
1 V Undefined R/W Overflow Flag
Set to 1 when an arithmetic overflow occurs, and
cleared to 0 otherwise.
0 C Undefined R/W Carry Flag
Set to 1 when a carry occurs, and cleared to 0
otherwise. Used by:
• Add instructions, to indicate a carry
• Subtract instructions, to indicate a borrow
• Shift and rotate instructions, to indicate a carry
The carry flag is also used as a bit accumulator by bit
manipulation instructions.
2.4.5 Initial Register Values
Reset exception handling loads the CPU’s program counter (PC) from the vector table, clears the
trace (T) bit in EXR to 0, and sets the interrupt mask (I) bits in CCR and EXR to 1. The other
CCR bits and the general registers are not initialized. Note that the stack pointer (ER7) is
undefined. The stack pointer should therefore be initialized by an MOV.L instruction executed
immediately after a reset.
2.5 Data Formats
The H8S/2000 CPU can process 1-bit, 4-bit BCD, 8-bit (byte), 16-bit (word), and 32-bit
(longword) data. Bit-manipulation instructions operate on 1-bit data by accessing bit n (n = 0, 1, 2,
…, 7) of byte operand data. The DAA and DAS decimal-adjust instructions treat byte data as two
digits of 4-bit BCD data.