The clock input (OSC1/CLKIN pin) is internally divided by four to generate four non-overlapping quadrature clocks namely Q1, Q2, Q3 and Q4. Internally, the program counter (PC) is incremented every Q1 if Reverse Engineering Microcontroller PIC16C558A Eeprom, the instruction is fetched from the program memory and latched into the instruction register in Q4. The instruction is decoded and executed during the following Q1 through Q4..
An “Instruction Cycle” consists of four Q cycles (Q1, Q2, Q3 and Q4). The instruction fetch and execute are pipelined such that fetch takes one instruction cycle while decode and execute takes another instruction cycle similar to the process of Reverse Engineering Microcontroller PIC16F73 Program.
Reverse Engineering Microcontroller PIC16C558A Eeprom
However, due to the pipelining, each instruction effectively executes in one cycle. If an instruction causes the program counter to change (e.g., GOTO) then two cycles are required to complete the instruction (Example 3-1) after Reverse engineering Microcontroller. A fetch cycle begins with the program counter (PC) incrementing in Q1.
In the execution cycle, the fetched instruction is latched into the “Instruction Register (IR)” in cycle Q1. This instruction is then decoded and executed during the Q2, Q3, and Q4 cycles. Data memory is read during Q2 (operand read) and written during Q4 (destination write).
The PIC16C55X(A) has a 13-bit program counter capable of addressing an 8K x 14 program memory space. Only the first 512 x 14 (0000h – 01FFh) for the PIC16C554(A), 1K x 14 (0000h – 03FFh) for the PIC16C556A and 2K x 14 (0000h – 07FFh) for the PIC16C558(A) are physically implemented.
Accessing a location above these boundaries will cause a wrap-around within the first 512 x 14 space PIC16C554(A) or 1K x 14 space PIC16C556A or 2K x 14 space PIC16C558(A). The reset vector is at 0000h and the interrupt vector is at 0004h when Recover MCU PIC16F74A Binary.
The data memory (Figure 4-4 and Figure 4-5) is partitioned into two Banks which contain the general purpose registers and the special function registers. Bank 0 is selected when the RP0 bit is cleared. Bank 1 is selected when the RP0 bit (STATUS <5>) is set.
The Special Function Registers are located in the first 32 locations of each Bank. Register locations 20-6Fh (Bank0) on the PIC16C554(A)/556A and 20-7Fh (Bank0) and A0-BFh (Bank1) on the PIC16C558(A) are general purpose registers implemented as static RAM when Reverse Engineering Microcontroller PIC16C558A Eeprom. Some special purpose registers are mapped in Bank 1