We can Extract Source Code of Encrypted Microcontroller dsPIC30F4011, please view the Microcontroller dsPIC30F4011 features for your reference:

The Stop condition begins with SDA asserted low.When SDA is sampled low, the SCL pin is allowed to float. When the pin is sampled high (clock arbitration), the Baud Rate Generator is loaded with SSPADD<6:0> and counts down to 0. After the BRG times out, SDA is sampled. If SDA is sampled low, a bus collision has occurred.

This is due to another master attempting to drive a data ‘0’ (Figure 17-31). If the SCL pin is sampled low before SDA is allowed to float high, a bus collision occurs. This is another case of another master attempting to drive a data ‘0’ when extract code from MCU.

The Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) module is one of the two serial I/O modules. (Generically, the USART is also known as a Serial Communications Interface or SCI.) The EUSART can be configured as a full-duplex asynchronous system that can communicate with peripheral devices, such as CRT terminals and personal computers. It can also be configured as a half-duplex synchronous system that can communicate with peripheral devices, such as A/D or D/A integrated circuits, serial EEPROMs, etc.
The Enhanced USART module implements additional features, including automatic baud rate detection and
calibration, automatic wake-up on Sync Break reception and 12-bit Break character transmit. These make it
ideally suited for use in Local Interconnect Network bus (LIN bus) systems if the chip’s firmware can be extracted.
The EUSART can be configured in the following modes:

• Asynchronous (full duplex) with:

– Auto-wake-up on character reception

– Auto-baud calibration

– 12-bit Break character transmission

• Synchronous – Master (half duplex) with selectable clock polarity
• Synchronous – Slave (half duplex) with selectable clock polarity

The operation of the Enhanced USART module is controlled through three registers:

• Transmit Status and Control (TXSTA)
• Receive Status and Control (RCSTA)
• Baud Rate Control (BAUDCON) before the program of IC has been extracted

These are detailed on the following pages in Register 18-1, Register 18-2 and Register 18-3, respectively.

The BRG is a dedicated 8-bit or 16-bit generator that supports both the Asynchronous and Synchronous modes of the EUSART. By default, the BRG operates in 8-bit mode; setting the BRG16 bit (BAUDCON<3>) selects 16-bit mode. The SPBRGH:SPBRG register pair controls the period of a free running timer. In Asynchronous mode, bits BRGH (TXSTA<2>) and BRG16 (BAUDCON<3>) also control the baud rate. In Synchronous mode, BRGH is ignored. Table 18-1 shows the formula for computation of the baud rate for different EUSART modes which only apply in Master mode (internally generated clock) after extract microprocessor’s software.

Given the desired baud rate and FOSC, the nearest integer value for the SPBRGH:SPBRG registers can be calculated using the formulas in Table 18-1. From this,the error in baud rate can be determined. An example calculation is shown in Example 18-1. Typical baud rates and error values for the various Asynchronous modes are shown in Table 18-2. It may be advantageous to use the high baud rate (BRGH = 1) or the 16-bit BRG to reduce the baud rate error, or achieve a slow baud rate for a fast oscillator frequency. Writing a new value to the SPBRGH:SPBRG registers causes the BRG timer to be reset (or cleared). This ensures the BRG does not wait for a timer overflow before outputting the new baud rate when break IC.