KS57C2308/P2308/C2316/P2316

SAM47 INSTRUCTION SET

 

 

REF — Reference Instruction

REF

Operation:

dst

Operand

 

Operation Summary

Bytes

Cycles

 

 

 

 

 

memc

Reference code

 

1

1 (note)

NOTE: The instruction referenced by REF determines the instruction cycles.

Description: The REF instruction is used to rewrite into 1-byte form, arbitrary 2-byte or 3-byte instructions (or two 1-byte instructions) stored in the REF instruction reference area in program memory. REF reduces the number of program memory accesses for a program.

Operand

 

 

Binary Code

 

 

Operation Notation

 

 

 

 

 

 

 

 

 

 

memc

t7

t6

t5

t4

t3

t2

t1

t0

PC13–0 memc.5–0 + (memc +

 

 

 

 

 

 

 

 

 

1).7–0

 

 

 

 

 

 

 

 

 

 

TJP and TCALL are 2-byte pseudo-instructions that are used only to specify the reference area:

1.When the reference area is specified by the TJP instruction, memc.7–6 = 00

PC13–0 memc.5–0 + (memc + 1).7–0

2.When the reference area is specified by the TCALL instruction, memc.7–6 = 01

(SP–4) (SP–1) (SP–2) PC12–0 SP–3 EMB, ERB, PC13–12 PC13–0 memc.5–0 + (memc + 1).7–0 SP SP–4

When the reference area is specified by any other instruction, the “memc” and “memc + 1” instructions are executed.

Instructions referenced by REF occupy 2 bytes of memory space (for two 1-byte instructions or one 2-byte instruction) and must be written as an even number from 0020H to 007FH in ROM. In addition, the destination address of the TJP and TCALL instructions must be located with the 3FFFH address. TJP and TCALL are reference instructions for JP/JPS and CALL/CALLS.

If the instruction following a REF is subject to the “redundancy effect”, the redundant instruction is skipped. If, however, the REF follows a redundant instruction, it is executed.

On the other hand, the binary code of a REF instruction is 1 byte. The upper 4 bits become the higher address bits of the referenced instruction, and the lower 4 bits of the referenced instruction becomes the lower address, producing a total of 8 bits or 1 byte (see Example 3 below).

NOTE

If the MSB value of the first one-byte binary code in instruction is “0”, the instruction cannot be referenced by a REF instruction.

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Samsung KS57C2308 manual REF Reference Instruction, Operand Operation Summary Bytes Cycles Memc Reference code