Reverse Microcontroller PIC12C508A structure and extract code from embedded mcu pic12c508a flash memory, decrypt the Firmware of pic12c508a microprocessor;

The clock recovery logic synchronizes internal clock to the incoming serial frames. Figure 87 illustrates the sampling process of the start bit of an incoming frame.

The sample rate is 16 times the baud rate for Normal mode, and eight times the baud rate for Double Speed mode. The horizontal arrows illustrate the synchronization variation due to the sampling process. Note the larger time variation when using the Double Speed mode (U2Xn = 1) of operation. Samples denoted zero are samples done when the RxDn line is idle (i.e., no communication activity).

Please shown in the figure. The clock recovery logic then uses samples 8, 9, and 10 for Normal mode, and samples 4, 5, and 6 for Double Speed mode (indicated with sample numbers inside boxes on the figure), to decide if a valid start bit is received.

If two or more of these three samples have logical high levels (the majority wins), the start bit is rejected as a noise spike and the Receiver starts looking for the next high to low-transition.

If however, a valid start bit is detected, the clock recovery logic is synchronized and the data recovery can begin. The synchronization process is repeated for each start bit before Breaking IC.

When the receiver clock is synchronized to the start bit, the data recovery can begin. The data recovery unit uses a state machine that has 16 states for each bit in Normal mode and eight states for each bit in Double Speed mode.

Figure 88 shows the sampling of the data bits and the parity bit. Each of the samples is given a number that is equal to the state of the recovery unit.The decision of the logic level of the received bit is taken by doing a majority voting of the logic value to the three samples in the center of the received bit when Restore IC program.

The center samples are emphasized on the figure by having the sample number inside boxes. The majority voting process is done as follows: If two or all three samples have high levels, the received bit is registered to be a logic 1.

If two or all three samples have low levels, the received bit is registered to be a logic 0. This majority voting process acts as a low pass filter for the incoming signal on the RxDn pin.

The recovery process is then repeated until a complete frame is received. Including the first stop bit. Note that the Receiver only uses the first stop bit of a frame.

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