UPD78F0138 NEC, UPD78F0138 Datasheet - Page 78

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

3.3 Instruction Address Addressing
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 information is set to the PC and branched by
the following addressing (for details of instructions, refer to 78K/0 Series Instructions User’s Manual (U12326E).
3.3.1 Relative addressing
78
An instruction address is determined by program counter (PC) contents and is normally incremented (+1 for each
[Function]
[Illustration]
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) and branched.
displacement value is treated as signed two’s complement data (−128 to +127) and bit 7 becomes a sign bit.
In other words, relative addressing consists of relative branching from the start address of the following
instruction to the −128 to +127 range.
This function is carried out when the BR $addr16 instruction or a conditional branch instruction is executed.
PC
When S = 0, all bits of
When S = 1, all bits of
15
15
15
are 0.
are 1.
8
PC
+
CHAPTER 3 CPU ARCHITECTURE
7
S
User’s Manual U16228EJ2V0UD
6
jdisp8
0
0
0
...
PC indicates the start address
of the instruction after the BR instruction.
The