Datasheet

Section 2 CPU
Rev. 4.00 Sep 27, 2006 page 46 of 1130
REJ09B0327-0400
Free area
Stack area
SP (ER7)
Figure 2.9 Stack
2.4.3 Control Registers
The control registers are the 24-bit program counter (PC), 8-bit extended control register (EXR),
and 8-bit condition-code register (CCR).
(1) 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.)
(2) Extended Control Register (EXR)
An 8-bit register. In this LSI, this register does not affect operation.
Bit 7—Trace Bit (T): This bit is reserved. In this LSI, this bit does not affect operation.
Bits 6 to 3—Reserved: These bits are reserved. They are always read as 1.
Bits 2 to 0—Interrupt Mask Bits (I2 to I0): These bits are reserved. In this LSI, these bits do not
affect operation.