IBM EM78P809N manual Instruction Set, Vdd 40KR2

Vdd

EM78P809N

/RESET

EM78P809N

8-Bit Microcontroller

Vdd

R1

Q1

40KR2

Fig 37. Residue Voltage Protection Circuit 2

4.19 Instruction Set

Each instruction in the instruction set is a 13-bit word divided into an OP code and one or more operands. Normally, all instructions are executed within one single instruction cycle (one instruction consists of 2 oscillator periods), unless the program counter is changed by instruction "MOV R2,A", "ADD R2,A", or by instructions of arithmetic or logic operation on R2 (e.g. "SUB R2,A", "BS(C) R2,6", "CLR R2", ⋅⋅⋅⋅). In this case, the execution takes two instruction cycles.

In case the instruction cycle specification is not suitable for certain applications, try to modify the instruction as follows:

(A)Change one instruction cycle to consist of 4 oscillator periods.

(B)The following commands are executed within two instruction cycles; "JMP", "CALL", "RET", "RETL", "RETI", including the conditional skip ("JBS", "JBC", "JZ", "JZA", "DJZ", "DJZA") instructions. In addition, instructions that are written to the program counter are executed within two instruction cycles.

Case (A) is selected by the CODE Option bit, called CLK. One instruction cycle consists of two oscillator clocks if CLK is low, and four oscillator clocks if CLK is high.

Note that once the 4 oscillator periods within one instruction cycle is selected as in Case (A), the internal clock source to TCC should be CLK=Fosc/4, not Fosc/2.

Furthermore, the instruction set has the following features:

(1)Every bit of any register can be set, cleared, or tested directly.

(2)The I/O register can be regarded as general register. That is, the same instruction can operate on I/O register.

The symbol "R" represents a register designator that specifies which one of the registers (including operational registers and general purpose registers) is to be utilized by the instruction. "b" represents a bit field designator that selects the value for the bit which is located in the register "R", and affects the operation. "k" represents an 8 or 10-bit constant or literal value.

Product Specification (V1.0) 07.26.2005 • 61

(This specification is subject to change without further notice)