CHAPTER 3 CPU ARCHITECTURE
User’s Manual U17446EJ3V1UD
39
Table 3-3. Special Function Registers (3/3)
Number of Bits Manipulated
Simultaneously
Address
Special Function Register (SFR) Name
Symbol
R/W
1 Bit
8 Bits
16 Bits
After Reset
FFEDH
External interrupt mode register 1
INTM1
−
√
−
00H
FFF3H
Preprocessor clock control register
PPCC
√
√
−
02H
FFF4H
Oscillation stabilization time select register
OSTS
−
√
−
Undefined
Note
FFFBH
Processor clock control register
PCC
R/W
√
√
−
02H
Note
The oscillation stabilization time that elapses after release of reset is selected by the option byte. For
details, refer to
CHAPTER 18 OPTION BYTE
.
3.3 Instruction Address Addressing
An instruction address is determined by the program counter (PC) contents. The PC contents are normally
incremented (+1 for each byte) automatically according to the number of bytes of an instruction to be fetched each
time another instruction is executed. When a branch instruction is executed, the branch destination address
information is set to the PC to branch by the following addressing (for details of each instruction, refer to
78K/0S
Series Instructions User’s Manual (U11047E)
).
3.3.1 Relative addressing
[Function]
The value obtained by adding 8-bit immediate data (displacement value: jdisp8) of an instruction code to the start
address of the following instruction is transferred to the program counter (PC) to branch. The displacement
value is treated as signed two’s complement data (–128 to +127) and bit 7 becomes the sign bit. In other words,
the range of branch in relative addressing is between –128 and +127 of the start address of the following
instruction.
This function is carried out when the BR $addr16 instruction or a conditional branch instruction is executed.
[Illustration]
15
0
PC
15
0
S
15
0
PC
+
8
7
6
α
jdisp8
When S = 0,
α
indicates that all bits are “0”.
... PC is the start address of
the next instruction of
a BR instruction.
When S = 1,
α
indicates that all bits are “1”.
Содержание 78K0S/KB1+
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