Altera SerialLite II Protocol - Manual (Page 73)

Altera Corporation 73
SerialLite II Protocol Reference Manual
SerialLite II Specification
■ CRC error
■ Unexpected channel number
■ Out of order packet
■ Out of order acknowledgment (if retry-on-error is enabled)
Action
If the data errors originated from a priority packet and if the retry-on-
error option is enabled, the SerialLite II receiver requests the
retransmission of that packet. Otherwise, if the data error originated from
data packets or priority packets without the retry-on-error option
enabled, the received packet is marked as bad (by asserting an error
signal on the user side interface) and forwarded to the user logic.
Data Error Threshold
The error threshold mechanism is implemented to detect an excessive
incidence of data errors. SerialLite II uses the ‘leaky bucket algorithm’.
Leaky Bucket Algorithm
The leaky bucket algorithm has the following rules:
1. When a data error is received, the error-threshold counter is
incremented by one.
2. The error-threshold counter is decremented by one every sixteen
columns until it reaches zero.
3. The decrement event can be free running and not synchronized to
internal operation or link state.
4. The data error threshold is exceeded when the error threshold
counter is greater than or equal to four.
Data Error Threshold Rules
The following rules must be followed when implementing the data error
threshold mechanism:
1. The data error threshold mechanism is only enabled in the link-up
state.
2. The data error threshold mechanism is disabled and cleared when
not in the link-up state.