Datasheet

Section 2 CPU
Page 38 of 982 REJ09B0465-0300 Rev. 3.00
Sep 17, 2010
H8S/20103, H8S/20203, H8S/20223, H8S/20115, H8S/20215, H8S/20235 Group
• U (user bit)
This bit can be written to and read from by software using the LDC, STC, ANDC, ORC, and
XORC instructions.
• N (negative bit)
This bit stores the value of the most significant bit of data as a sign bit.
• C (carry flag)
This flag is 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.