EM78P809N
8-Bit Microcontroller
Vdd
Vdd
R1
R2
EM78P809N
/RESET
Q1
40K
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)
ELAN [ ELAN MICROELECTRONICS CORP ]
