Clocking in GTZ
The clocking scheme in GTZ is different from clocking schemes in other GTs. The basis of USRCLK routing
is vertical GCLK spines that run through multiple SLRs (depending on the device size).
There are a total of 32 vertical GCLK lines available in GTZ, with up to 16 GTZ channels in which 8 GTZ
channels are located on the North GTZ die, and the other 8 GTZ channels on South die. The vertical GCLK
line that drives TXUSRCLK or RXUSRCLK clock inputs to both GTZ dies need to be shared between the 16
GTZ channels.
GCLK Spines
Table 1 below shows the assignment of vertical GCLK lines to GTZ clocks.
GCLK spine #
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
GTZ North
TXOUTCLK0
TXUSRCLK0
TXOUTCLK1
TXUSRCLK1
TXUSRCLK2
TXUSRCLK3
RXOUTCLK0
RXUSRCLK0
RXOUTCLK1
RXUSRCLK1
RXOUTCLK2
RXUSRCLK2
RXOUTCLK3
RXUSRCLK3
DRPCLK0
CFGCLK
Unused
DRPCLK1
RXUSRCLK7
NC
RXUSRCLK6
NC
RXUSRCLK5
NC
RXUSRCLK4
NC
TXUSRCLK7
GTZ South
NC
TXUSRCLK4
NC
TXUSRCLK5
TXUSRCLK6
TXUSRCLK7
NC
RXUSRCLK4
NC
RXUSRCLK5
NC
RXUSRCLK6
NC
RXUSRCLK7
DRPCLK1
CFGCLK
Unused
DRPCLK0
RXUSRCLK3
RXOUTCLK3
RXUSRCLK2
RXOUTCLK2
RXUSRCLK1
RXOUTCLK1
RXUSRCLK0
RXOUTCLK0
TXUSRCLK3
Direction at GTZ die
Output
Input
Output
Input
Input
Input
Output
Input
Output
Input
Output
Input
Output
Input
Input
Input
Input
Input
Input
Output
Input
Output
Input
Output
Input
Output
Input
27
28
29
30
31
TXUSRCLK6
TXUSRCLK5
NC
TXUSRCLK4
NC
TXUSRCLK2
TXUSRCLK1
TXOUTCLK1
TXUSRCLK0
TXOUTCLK0
Input
Input
Output
Input
Output
Table 1: GCLK Spine assignments
The OUTCLKs are marked in red to show they need to be routed to either BUFG_LB or BUFGCTRL to be
used as USRCLKs.
Figure 1 below shows the high level view of GCLK spines.
GTZ North
0
5 6
7 8 9 10
1213 14
1516 171819 2021 22
23 2425 26
4 xGTZ
4 xGTZ
GTZ South
Figure 1: GCLK Spines
MIB 7
MIB 0
Unused
27 2829 30 31
MIB 1
MIB 2
MIB 3
Input to
GTZ
MIB 6
MIB 5
MIB 4
MIB 3
11
MIB 4
MIB 5
MIB 6
Output from
GTZ
MIB 7
Legend
1 2 3 4
4 xGTZ
MIB 2
MIB 1
MIB 0
4 xGTZ
Resources required
The OUTCLK/MMCM clock can be used as usrclk only via either BUFG_LB(only for OUTCLK) or
BUFGCTRL. The diagrams below are in the 7 Series GTZ User Guide UG478 in the GTZ lounge.
Figure 2: User Clock routing
BUFGCTRL
Each GCLK spine is sub divided in segments to allow user some flexibility. The following figure is a
representation of XC7VH870T device SLRs and GTZs. Each column represents the USRCLK spine with
possible BUFGCTRLs location.
TXUSRCLK0 TXUSRCLK1 TXUSRCLK2 TXUSRCLK3 RXUSRCLK0 RXUSRCLK1 RXUSRCLK2 RXUSRCLK3 DRPCLK0 DRPCLK1 RXUSRCLK7 RXUSRCLK6 RXUSRCLK5 RXUSRCLK4 TXUSRCLK7 TXUSRCLK6 TXUSRCLK5 TXUSRCLK4
BUFGCTRL_X0Y
65
67
68
69
71
73
75
77
78
81
82
84
86
88
90
91
92
94
SLR close to North Octal
BUFGCTRL_X0Y
33
35
36
37
39
41
43
45
46
49
50
52
54
56
58
59
60
62
Middle SLR
BUFGCTRL_X0Y
1
3
4
5
7
9
11
13
14
17
18
20
22
24
26
27
28
30
SLR close to South Octal
TXUSRCLK4 TXUSRCLK5 TXUSRCLK6 TXUSRCLK7 RXUSRCLK4 RXUSRCLK5 RXUSRCLK6 RXUSRCLK7 DRPCLK1 DRPCLK0 RXUSRCLK3 RXUSRCLK2 RXUSRCLK1 RXUSRCLK0 TXUSRCLK3 TXUSRCLK2 TXUSRCLK1 TXUSRCLK0
Figure 3: BUFGCTRL locations
The selection of BUFGCTRL is based on the usage. Zooming into column1 (TXUSRCLK0 on North and
TXUSRCLK4 on south) the diagram looks like the figure below:
TXUSRCLK0
BUFGCTRL_X0Y
65
SLR close to North Octal
BUFGCTRL_X0Y
33
Middle SLR
BUFGCTRL_X0Y
1
SLR close to South Octal
TXUSRCLK4
Figure 4: Zooming in one of the USRCLK spine
Depending on the logic/MMCM placement an appropriate BUFGCTRL has to be used. If MMCM is near
south Octal then BUFGCTRL_X0Y1 has to be used, if in the middle SLR BUFGCTRL_X0Y33 and
BUFGCTRL_X0Y65 if near north octal.
Figures below show the scenarios the clock can be routed and the spine can be segmented.
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
GTZ
(A)
(B)
(C)
(D)
(E)
(F)
(G)
Figure 5: Routing scenarios
Fig A – Unrouted spine with 3 BUFGCTRLs
Fig B – MMCM/logic place near south octal uses bottom BUFGCTRL and MMCM/logic placed near north
octal uses top BUFGCTRL. The BUFGCTRL in the middle is unused.
Fig C – Center BUFG clocks the top octal and bottom BUFG clocks the south.
Fig D, E, F and G are similar with different scenarios.