21-01-2016, 04:09 PM
The 8085 is an 8-bit general purpose microprocessor that can address 216 =64K Byte of memory. It has 40 pins and uses +5V for power. It can run at a maximum frequency of 3 MHz.
The pins on the chip can be grouped into 6 groups:
Address Bus.
Data Bus.
Control and Status Signals.
Power supply and frequency.
Externally Initiated Signals.
Serial I/O ports.
Functional Blocks
Registers
ALU
Instruction Decoder
Address Buffer
Address/Data Buffer
Increment/ Decrement Address Latch
Interrupt Control
Serial I/O Control
Timing and control circuitry
Registers
General purpose Registers
Temporary Registers
Special Purpose Register
16 Bit Registers
The Flags register
There is also the flags register whose bits are affected by the arithmetic & logic operations.
S-sign flag The sign flag is set if bit D7 of the accumulator is set after an arithmetic or logic operation.
0- + Ve 1- -Ve
Z-zero flag
Set if the result of the ALU operation is 0. Otherwise is reset. This flag is affected by operations on the accumulator as well as other registers. (DCR B).
AC-Auxiliary Carry
This flag is set when a carry is generated from bit D3 and passed to D4 . This flag is used only internally for BCD operations.
P-Parity flag
After an ALU operation if the result has an even no of 1’s the p-flag
CY-carry flag
CY = carry is set when result generates a carry. Also a borrow flag.