HD64F3694FXV Datasheet, PDF (49/452 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 2 CPU
General register ER7 has the function of stack pointer (SP) in addition to its general-register
function, and is used implicitly in exception handling and subroutine calls. Figure 2.4 shows the
relationship between stack pointer and the stack area.
SP (ER7)
Free area
Stack area
Figure 2.4 Relationship between Stack Pointer and Stack Area
2.2.2 Program Counter (PC)
This 24-bit counter indicates the address of the next instruction the CPU will execute. The length
of all CPU instructions is 2 bytes (one word), so the least significant PC bit is ignored. (When an
instruction is fetched, the least significant PC bit is regarded as 0). The PC is initialized when the
start address is loaded by the vector address generated during reset exception-handling sequence.
2.2.3 Condition-Code Register (CCR)
This 8-bit register contains internal CPU status information, including an interrupt mask bit (I) and
half-carry (H), negative (N), zero (Z), overflow (V), and carry (C) flags. The I bit is initialized to 1
by reset exception-handling sequence, but other bits are not initialized.
Some instructions leave flag bits unchanged. Operations can be performed on the CCR bits by the
LDC, STC, ANDC, ORC, and XORC instructions. The N, Z, V, and C flags are used as branching
conditions for conditional branch (Bcc) instructions.
For the action of each instruction on the flag bits, see appendix A.1, Instruction List.
Rev.5.00 Nov. 02, 2005 Page 19 of 418
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