TMS320C3X REGISTERS
The CPU registers contained in the TMS320C31 chip are described below:

R0 - R7	eight 40-bit registers that allow for extended-precision results. These registers can store 32-bit integer and 40-bit floating-point numbers
AR0 - AR7	eight general-purpose auxiliary registers that are commonly used for indirect memory addressing
IR0	indexing registers for indexing an address
ST	status register; provides information on the status of the CPU.
SP	stack pointer that contains the address of the top of the stack
BK	block size register that is used to specify the block size of a circular buffer
IE, IF, and IOF	interrupt enable register, interrupt flag register and I/O flag register respectively
RC	repeat count register that is used to specify the number of times a block of code is to be executed
RS, RE	registers that contain the starting and ending addresses of a block of code to be executed respectively
PC	program counter that contains the address of the next instruction to be fetched
DP	data page register that specifies one of 256 data pages, each page with 64k words

Additional information and description can be found in the laboratory textbook:

R. Chassaing, et al, Digital Signal Processsing: Laboratory Experiments Using C and the TMS320C31 DSK, John Wiley and Sons, Inc., ISBN 0471293628, 1999.