em78p862a ELAN Microelectronics Corp, em78p862a Datasheet - Page 34

• Manufacturer Part Number: em78p862a
• Description: 8-bit Risc Type Microprocessor
• Manufacturer: ELAN Microelectronics Corp

EM78862B
8-Bit RISC Type Microprocessor
28 of 35
08.02.2004 (V1.0)
6.9
The EM78862B IC is equipped with one CODE option register that is not a part of the normal
program memory. The option bits cannot be accessed during normal program execution.
Bit 0, 5, 6, 7, & 10: Reserved. Set these bits to “1”
Bit 2, 3, 4, 8, & 9: Reserved. Clear these bits to “0”
Bit 1: (MCLK) Main Clock select
Bit 11: (OSCSEL) Oscillator select
The RC or crystal oscillator is selected by OSCSEL bit of code option.
6.10 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
instructions "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," etc.). Under this condition, the execution
takes two instruction cycles.
If for some reasons, the specification of the instruction cycle is not suitable for certain
applications, try modifying the instruction as follows:
a) Change one instruction cycle to consist of 4 oscillator periods.
b) Execute within two instruction cycles, "JMP," "CALL," "RET," "RETL," & "RETI," or the
Furthermore, the instruction set has the following features:
The symbol "R" in the instruction set 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 operation. "K" represents an 8 or 10-bit constant or
literal value.
OSCSEL
Bit 11
Every bit of any register can be set, cleared, or tested directly.
The I/O register can be regarded as general register. That is, the same instruction can
operate on I/O register.
conditional skip ("JBS," "JBC," "JZ," "JZA," "DJZ," & "DJZA") instructions which were
tested to be true. Also execute within two instruction cycles the instructions that are
written to the program counter.
0: 3.579MHz
1: 1.7895MHz
0: RC mode
1: Crystal mode
Code Options
Bit 0
1
Bit 9
0
Bit 8
0
Bit 7
1
Bit 6
1
This specification is subject to change without further notice.
Bit 5
1
Bit 4
0
Bit 3
0
Bit 2
0
MCLK
Bit 1
Bit 0
1