184
Virtex-5 RocketIO GTP Transceiver User Guide
UG196 (v1.3) May 25, 2007
Chapter 7:
GTP Receiver (RX)
R
shows how RXDATA is received serially when the internal datapath is eight
bits (INTDATAWIDTH = 0) and 8B/10B decoding is disabled.
shows how RXDATA is received serially when the internal datapath is 10 bits
(INTDATAWIDTH =
1
) and 8B/10B decoding is disabled. When RXDATA is 10 bits or 20
bits wide, the RXDISPERR and RXCHARISK ports are taken from the 8B/10B decoder
interface and are used to present the extra bits.
When 8B/10B decoding is used, the data interface is a multiple of 8 bits like in
,
but the data is decoded before it is presented at the RXDATA port. Refer to
for more details about bit ordering when using 8B/10B
decoding.
Connecting RXUSRCLK and RXUSRCLK2
The FPGA RX Interface includes two parallel clocks: RXUSRCLK and RXUSRCLK2.
RXUSRCLK is the internal clock for the PCS logic in the GTP receiver. The required rate for
RXUSRCLK depends on the internal datapath width of the GTP_DUAL tile
(INTDATAWIDTH), and the RX line rate of the GTP receiver (see
to see how RX line rate is determined).
shows how to
calculate the required rate for RXUSRCLK.
Equation 7-7
RXUSRCLK2 is the main synchronization clock for all signals into the RX side of the GTP
transceiver. Most signals into the RX side of the GTP receiver are sampled on the positive
edge of RXUSRCLK2. RXUSRCLK2 is the same rate at RXUSRCLK when RXDATAWIDTH
Figure 7-34:
RX Interface with 8B/10B Bypassed (8-Bit Internal Datapath)
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
RXDATA
W
IDTH = 1
I
N
TDATA
W
IDTH = 0 and RXDEC8B10BUSE = 0
RXDATA
RXDATA
W
IDTH = 0
UG196_c7_31_100506
Recei
v
ed
Last
Recei
v
ed
Last
Recei
v
ed
First
Recei
v
ed
First
Figure 7-35:
RX Interface with 8B/10B Bypassed (10-Bit Internal Datapath)
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
RXDATA
W
IDTH = 1
RXDATA
RXDATA
W
IDTH = 0
RXCHARISK[0]
RXDISPERR[0]
UG196_c7_32_100506
Recei
v
ed
Last
Recei
v
ed
Last
Recei
v
ed
First
Recei
v
ed
First
RXCHARISK[0]
RXDISPERR[0]
RXCHARISK[1]
RXDISPERR[1]
I
N
TDATA
W
IDTH = 1 and RXDEC8B10BUSE = 0
RXUSRCLK Rate
Line Rate
Internal Datapath Width
-----------------------------------------------------------------
=