+ // TODO: Service Request(Srq):
+ // Device holds low part of comannd stopbit for 140-260us
+ //
+ // Command:
+ // ......._ ______________________ ___ ............_ -------
+ // | | | | | | |
+ // Command | | | | | Data bytes | |
+ // ........|___| | 140-260 |__| |_............|___|
+ // |stop0 | Tlt Stop-to-Start |start1| |stop0 |
+ //
+ // Command without data:
+ // ......._ __________________________
+ // | |
+ // Command | |
+ // ........|___| | 140-260 |
+ // |stop0 | Tlt Stop-to-Start |
+ //
+ // Service Request:
+ // ......._ ______ ___ ............_ -------
+ // | 140-260 | | | | | |
+ // Command | Service Request | | | | Data bytes | |
+ // ........|___________________| |__| |_............|___|
+ // |stop0 | |start1| |stop0 |
+ // ......._ __________
+ // | 140-260 |
+ // Command | Service Request |
+ // ........|___________________|
+ // |stop0 |
+ // This can be happened?
+ // ......._ ______________________ ___ ............_ -----
+ // | | | | | | 140-260 |
+ // Command | | | | | Data bytes | Service Request |
+ // ........|___| | 140-260 |__| |_............|_________________|
+ // |stop0 | Tlt Stop-to-Start |start1| |stop0 |
+ //
+ // "Service requests are issued by the devices during a very specific time at the
+ // end of the reception of the command packet.
+ // If a device in need of service issues a service request, it must do so within
+ // the 65 µs of the Stop Bit’s low time and maintain the line low for a total of 300 µs."
+ //
+ // "A device sends a Service Request signal by holding the bus low during the low
+ // portion of the stop bit of any command or data transaction. The device must lengthen
+ // the stop by a minimum of 140 J.lS beyond its normal duration, as shown in Figure 8-15."
+ // http://ww1.microchip.com/downloads/en/AppNotes/00591b.pdf