The STS instruction is used to store data that are shifted serially into
the PHY layer shift register to the system bus address space. The STS
instruction is based on direct addressing, and the address must be given as an operand
to the instruction for the data transfer to start. The address is the first set of
operands, and data are the second set. The size of the address and data operands are
given by the size fields presented in Figure 1. The maximum size for both address and data is 32 bits.
The 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 Figure 1, 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 have been successfully transferred.