User data phase – Altera JESD204B IP User Manual
Page 44
Configura‐
tion Octet
Bits
Description
MSB
6
5
4
3
2
1
LSB
11
RES1[7:0]
RES1 = Reserved. Set to 8'h00
12
RES2[7:0]
RES2 = Reserved. Set to 8'h00
13
FCHK[7:0]; automatically calculated using run-time
configuration.
FCHK is the modulus 256 of the
sum of the 13 configuration octets
above.
If you change any of the octets
during run-time, make sure to
update the new FCHK value in the
register.
The JESD204 TX IP core also supports debug feature to continuously stay in ILAS phase without exiting.
You can enable this feature by setting the bit in
csr_ilas_loop
register. There are two modes of entry:
• RX asserts
SYNC_N
and deasserts it after CGS phase. This activity triggers the ILAS phase and the CSR
will stay in ILAS phase indefinitely until this setting changes.
• Link reinitialization through CSR is initiated. The JESD204B IP core transmits /K/ character and
causes the RX converter to enter CGS phase. After RX deasserts
SYNC_N
, the CSR enters ILAS phase
and will stay in that phase indefinitely until this setting changes.
In ILAS loop, the multi-frame transmission is the same where /R/ character (K28.0) marks the start of
multi-frame and /A/ character (K28.3) marks the end of multi-frame, with dummy data in between. The
dummy data is an increment of Dx.y.
User Data Phase
During the user data phase, character replacement at the end of frame and end of multi-frame is
opportunistically inserted so that there is no additional overhead for data bandwidth.
Character replacement for non-scrambled data
The character replacement for non-scrambled mode in the IP core follows these JESD204B specification
rules:
• At end of frame (not coinciding with end of multi-frame), which equals the last octet in the previous
frame, the transmitter replaces the octet with /F/ character (K28.7). However, if an alignment character
was transmitted in the previous frame, the original octet will be encoded.
• At the end of a multi-frame, which equals to the last octet in the previous frame, the transmitter
replaces the octet with /A/ character (K28.3), even if a control character was already transmitted in the
previous frame.
For devices that do not support lane synchronization, only /F/ character replacement is done. At every
end of frame, regardless of whether the end of multi-frame equals to the last octet in previous frame, the
transmitter encodes the octet as /F/ character (K28.7) if it fits the rules above.
UG-01142
2015.05.04
User Data Phase
4-7
JESD204B IP Core Functional Description
Altera Corporation