W78E054D Datasheet, PDF (13/89 Pages) List of Unclassifed Manufacturers – 8-bit microcontroller

W78E054D/W78E052D Data Sheet
The data pointer of W78E054D/W78E052D series is same as standard 8052 that have one 16-bit Da-
ta Pointer (DPTR).
7.7 Architecture
The W78E054D/W78E052D series are based on the standard 8052 device. It is built around an 8-bit
ALU that uses internal registers for temporary storage and control of the peripheral devices. It can ex-
ecute the standard 8052 instruction set.
7.7.1 ALU
The ALU is the heart of the W78E054D/W78E052D series. It is responsible for the arithmetic and logi-
cal functions. It is also used in decision making, in case of jump instructions, and is also used in calcu-
lating jump addresses. The user cannot directly use the ALU, but the Instruction Decoder reads the
op-code, decodes it, and sequences the data through the ALU and its associated registers to generate
the required result. The ALU mainly uses the ACC which is a special function register (SFR) on the
chip. Another SFR, namely B register is also used Multiply and Divide instructions. The ALU generates
several status signals which are stored in the Program Status Word register (PSW).
7.7.2 Accumulator
The Accumulator (ACC) is the primary register used in arithmetic, logical and data transfer operations
in the W78E054D/W78E052D series. Since the Accumulator is directly accessible by the CPU, most
of the high speed instructions make use of the ACC as one argument.
7.7.3 B Register
This is an 8-bit register that is used as the second argument in the MUL and DIV instructions. For all
other instructions it can be used simply as a general purpose register.
7.7.4 Program Status Word
This is an 8-bit SFR that is used to store the status bits of the ALU. It holds the Carry flag, the Auxiliary
Carry flag, General purpose flags, the Register Bank Select, the Overflow flag, and the Parity flag.
7.7.5 Scratch-pad RAM
The W78E054D/W78E052D series has a 256 byte on-chip scratch-pad RAM. This can be used by the
user for temporary storage during program execution. A certain section of this RAM is bit addressable,
and can be directly addressed for this purpose.
7.7.6 Stack Pointer
The W78E054D/W78E052D series has an 8-bit Stack Pointer which points to the top of the Stack.
This stack resides in the Scratch Pad RAM in the W78E054D/W78E052D. Hence the size of the stack
is limited by the size of this RAM.
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Publication Release Date: Jun 9, 2015
Revision A13