HD6412340 HITACHI [Hitachi Semiconductor], HD6412340 Datasheet - Page 52

• Manufacturer Part Number: HD6412340
• Description: H8S/2345 F-ZTAT Hardware Manual
• Manufacturer: HITACHI [Hitachi Semiconductor]

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 2.9 shows the
stack.
Free area
SP (ER7)
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): This 8-bit register contains the trace bit (T) and three
interrupt mask bits (I2 to I0).
Bit 7—Trace Bit (T): Selects trace mode. When this bit is cleared to 0, instructions are executed
in sequence. When this bit is set to 1, a trace exception is generated each time an instruction is
executed.
Bits 6 to 3—Reserved: These bits are reserved. They are always read as 1.
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