Intel 8080 microprocessor architecture
Program, data and stack memories occupy the same memory space. The total addressable memory size is 64 KB.
Program memory - program can be located anywhere in memory. Jump, branch and call instructions use 16-bit addresses, i.e. they can be used to jump/branch anywhere within 64 KB. All jump/branch instructions use absolute addressing.
Data memory - the processor always uses 16-bit addresses so that data can be placed anywhere.
Stack memory is limited only by the size of memory. Stack grows downward.
First 64 bytes in a zero memory page should be reserved for vectors used by RST instructions.
The processor supports maskable interrupts. When an interrupt occurs the processor fetches from the bus one instruction, usually one of these instructions:
The interrupts can be enabled or disabled using EI and DI instructions.
256 Input ports
Accumulator or A register is an 8-bit register used for arithmetic, logic, I/O and load/store operations.
Flag is an 8-bit register containing 5 1-bit flags:
Stack pointer is a 16 bit register. This register is always incremented/decremented by 2.
Program counter is a 16-bit register.
8080 instruction set consists of the following instructions:
Register - references the data in a register or in a register pair.
Register indirect - instruction specifies register pair containing address, where the data is located.
Immediate - 8 or 16-bit data.
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