W78E516DDG Datasheet, PDF (12/90 Pages) Nuvotem Talema – 8-BIT MICROCONTROLLER

W78E516D/W78E058D Data Sheet
as an internal timer, depending on the setting of bit C/T2 in T2CON. Timer 2 has three operating mod-
es: capture, auto-reload, and baud rate generator. The clock speed at capture or auto-reload mode is
the same as that of Timers 0 and 1.
7.4.1 Clock
The W78E516D/W78E058D series are designed to be used with either a crystal oscillator or an ex-
ternal clock. Internally, the clock is divided by two before it is used by default. This makes the
W78E516D/W78E058D series relatively insensitive to duty cycle variations in the clock.
7.5 Interrupts
The Interrupt structure in the W78E516D/W78E058D series is slightly different from that of the stan-
dard 8052. Due to the presence of additional features and peripherals, the number of interrupt sources
and vectors has been increased. The W78E516D/W78E058D series provides 8 interrupt resources
with two priority level, including four external interrupt sources, three timer interrupts, serial I/O inter-
rupts.
7.6 Data Pointers
The data pointer of W78E516D/W78E058D series is same as standard 8052 that have one 16-bit Da-
ta Pointer (DPTR).
7.7 Architecture
The W78E516D/W78E058D 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 W78E516D/W78E058D 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 W78E516D/W78E058D 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.
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