Look up table with data element promotion

A digital data processor comprising:

• an instruction memory storing instructions each specifying a data processing operation and at least one data operand field;
• an instruction decoder coupled to the instruction memory for sequentially recalling instructions from the instruction memory and determining the data processing operation and the at least one data operand;
• a data register file that includes a source register and a destination register;
• a memory configured to store a set of tables;
• and
• at least one operational unit coupled to the data register file, to the memory, and to the instruction decoder to perform a data processing operation upon at least one operand corresponding to an instruction decoded by the instruction decoder and store results of the data processing operation, wherein the at least one operational unit is configured to perform a table recall in response to a look up table read instruction by:
• recalling a set of data elements that includes an element from each table of the set of tables at a respective address specified by the source register, the recalled data elements having a first data size;
• and
• storing the set of data elements in successive slots in a destination register, wherein each element of the set of data elements is promoted to be stored in the destination register in a larger data size than the first data size;
• wherein:
• the data register file further includes a look up table configuration register having a size field that indicates the first data size and a field specifying a number of tables in the set of tables;
• and
• the look up table read instruction specifies the look up table configuration register.

A device comprising:

• a register file that includes a source index register, a table base address register, and a destination register;
• a memory configured to store a set of tables, wherein the table base address register is configured to store a base address for the set of tables, and the source index register is configured to store an index for each table of the set of tables;
• and
• an operational unit coupled to the register file and the memory, wherein the operational unit is configured to execute a look up table read instruction by:
• recalling a set of data elements that includes an element from each table of the set of tables at a respective address specified by a combination of the source index register and the table base address register, wherein each data element of the set of data elements has a first data size;
• promoting each data element of the set of data elements from the first data size to a second data size;
• and
• storing the set of data elements having the second data size in the destination register.