Inter-Byte Delay

When performing a multibyte transfer (LD combined with REPEAT) or reading out the System Information Block (SIB), the output data will come out in a continuous stream. Depending on the application, the data might come out too fast on the receiver side, and there might not be enough time for the data to be processed before the next Start bit arrives.

The inter-byte delay works by inserting a fixed number of Idle bits for multibyte transfers. The reason for adding an inter-byte delay is that there is no guard time inserted when all data is going in the same direction.

The inter-byte delay feature can be enabled by writing a ‘1’ to the Inter-Byte Delay Enable (IBDLY) bit in the Control A (UPDI.CTRLA) register. As a result, two extra Idle bits will be inserted between each byte to relax the sampling time for the debugger.
Figure 1. Inter-Byte Delay Example with LD and RPT
  1. 1.GT denotes the guard time insertion.
  2. 2.SB is for Stop bit.
  3. 3.IB is the inserted inter-byte delay.
  4. 4.The rest of the frames are data and instructions.