The Boundary Scan Register (BSR) contains a number of bits which correspond to active pins and associated control signals.
Each input/output pin corresponds to a 3-bit register in the BSR. The OUTPUT bit contains data that can be forced on the pad. The INPUT bit facilitates the observability of data applied to the pad. The CONTROL bit selects the direction of the pad.
For more information, refer to BDSL files available on www.microchip.com.