CHAPTER 4: INSTRUCTION SET

 

 

 

JR sign8

Jump to relative location sign8

1 cycle

Function: PC ← PC + sign8 + 1 (sign8 = -128~127)

Adds the relative address specified with the sign8 to the address next to this instruction, to unconditionally branch to that address. Branch destination range is the next address of this instruction -128 to +127.

Code:

Mnemonic

 

MSB

 

 

 

 

 

 

 

LSB

 

JR sign8

 

 

0

0

0

0

0

s7

s6

s5

s4

s3

s2

s1

s0

0000H–00FFH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flags:

E

I

C

 

Z

 

 

 

 

 

 

 

 

 

 

 

 

↓

–

–

 

–

 

 

 

 

 

 

 

 

 

 

 

 

Mode:

Signed 8-bit PC relative

 

 

 

 

 

 

 

 

 

 

 

Extended addressing: Valid

 

 

 

 

 

 

 

 

 

 

Extended

LDB

%EXT,imm8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

operation: JR

sign8

 

 

PC ← PC + sign16 + 1

(sign16 = -32768 to 32767, upper 8-bit: imm8, lower 8-bit: sign8)

JRC sign8

Jump to relative location sign8 if C flag is set

1 cycle

Function: If C = 1 then PC ← PC + sign8 + 1 (sign8 = -128~127)

Executes the "JR sign8" instruction if the C (carry) flag has been set to "1", otherwise executes the next instruction.

Code:

Mnemonic

 

MSB

 

 

 

 

 

LSB

 

JRC sign8

 

 

0

0

1

0

0

s7

s6

s5

s4

s3

s2

s1

s0

0400H–04FFH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Flags:

E

I

C

 

Z

 

 

 

 

 

 

 

 

 

 

 

 

 

↓

–

–

 

–

 

 

 

 

 

 

 

 

 

 

 

 

Mode:

Signed 8-bit PC relative

 

 

 

 

 

 

 

 

 

Extended addressing: Valid

 

 

 

 

 

 

 

 

Extended

LDB

%EXT,imm8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

operation: JRC

sign8

 

 

If C = 1 then PC ←

PC + sign16 + 1

 

 

 

(sign16 = -32768 to 32767, upper 8-bit: imm8, lower 8-bit: sign8)

S1C63000 CORE CPU MANUAL

EPSON

97