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S1C63000 CORE CPU MANUAL EPSON 13
CHAPTER 2: ARCHITECTURE
(2) Instruction with a 4-bit A register data that specifies a relative address
JR %A
This instruction branches the program sequence with the content of the A register as an unsigned
4-bit relative address. The range that can be branched is from the next instruction address +0 to
+15 (absolute value in the A register). This instruction is useful when operation results are used as
the 4-bit relative addresses.
Example:
LD %A,4
JR %A ...Jumps to the instruction 5 steps after
(3) Instruction with an 8-bit BA register data that specifies a relative address
JR %BA
This instruction branches the program sequence with the content of the BA register as an unsigned
8-bit relative address ( the B register data becomes the high-order 4 bits). The range that can be
branched is from the next instruction address +0 to +255 (absolute value in the BA register). This
instruction is useful when operation results are used as the 8-bit relative addresses.
Example:
LDB %BA,29
JR %BA ...Jumps to the instruction 30 steps after
(4) Instruction with a data memory address within 0000H to 003FH in which the content specifies a 4-bit
relative address
JR [addr6]
This instruction branches the program sequence with the content of the data memory specified by
the [addr6] as an unsigned 4-bit relative address. The operand [addr6] can specify a data memory
address within 0000H to 003FH. The range that can be branched is from the next instruction
address +0 to +15 (absolute value in the specified data memory). For the data memory area that is
specified with [addr6], bit operation instructions (CLR, SET, TST) are provided so that various
flags can be set simply. This jump instruction can be used as a conditional jump according to these
flags.
Example: When the content of the address 0010H is 4 (0100B).
SET [0x0010],0 ...Sets the bit 0 in the address 0010H to "1" ([0010H] = 5)
JR [0x0010] ...Jumps to the instruction 6 steps after
• Indirect jump instruction (JP)
The indirect jump instruction "JP %Y" loads the content of the Y register into the PC to branch to that
address unconditionally. This instruction can branch entire 64K program memory because the 16-bit
data in the Y register becomes a branch destination address as it is.
Example:
LDB %EXT,0x24
LDB %YL,0x00 ...Y = 2400H
JP %Y ...Jumps to the address 2400H
Figure 2.2.3.1 shows the operation of the jump instructions and the branch range.