The STS instruction is used to store data that is shifted
serially into the PHY layer to the bus matrix address space. The STS
instruction is based on direct addressing, where the address is the first set of
operands, and data is the second set. The size of the address and data operands are
given by the size fields presented in the figure below. The maximum size for both
address and data is 16 bits.
STS supports repeated memory access when combined with the
REPEAT instruction.
Figure 1. 
STS Instruction
Operation
The transfer protocol for an
STS instruction is depicted in the
figure as well, following this sequence: - 1.The address is sent.
- 2.An Acknowledge (ACK) is sent back from the UPDI if the transfer was successful.
- 3.The number of bytes as specified
in the
STSinstruction is sent. - 4.A new ACK is received after the data has been successfully transferred.