SLAU320AJ July 2010 – May 2021
The JTAG communication implemented on the MSP430 also supports access to a memory array in a more efficient manner. The instruction IR_DATA_QUICK is used to accomplish this operation. The R/W signal selects whether a read or write access is to be performed. Before this instruction can be loaded into the JTAG IR register, the program counter (PC) of the target MSP430 CPU must be set to the desired memory starting address. After the IR_DATA_QUICK instruction is shifted into the IR register, the PC is incremented by two with each falling edge of TCLK, automatically pointing the PC to the next memory location. The IR_DATA_QUICK instruction allows setting the corresponding MDB to a desired value (write), or captures (reads) the MDB with a DR_SHIFT16 operation. The MDB should be set when TCLK is low. On the next rising TCLK edge, the value on the MDB is written into the location addressed by the PC. To read a memory location, TCLK must be high before the DR_SHIFT16 operation is executed.