Renesas Hitachi H8S/2191, Hardware Manual, Page: 53 / 1065

Rev. 2.0, 11/00, page 26 of 1037
SP (ER7)
Free area
Stack area
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.
(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.
Bit 7: Interrupt Mask Bit (I)
Masks interrupts other than NMI when set to 1. (NMI is accepted regardless of the I bit
setting.) The I bit is set to 1 by hardware at the start of an exception-handling sequence.
For details, see section 6, Interrupt Controller.