72
Lucent Technologies Inc.
Preliminary Data Sheet, Rev. 1
ORCA Series 3 FPGAs
September 1998
Programmable Clock Manager (PCM):
Advance Information (continued)
Delay-Locked Loop (DLL) Mode
DLL mode is used for implementing a delayed clock
(phase adjustment), clock doubling, and duty cycle
adjustment. All DLL functions stem from a delay line
with 32 taps. The delayed input clock is pulled from
various taps and processed to implement the desired
result. There is no feedback clock in DLL mode, provid-
ing a very stable output and a fast lock time for the out-
put clock.
DLL mode is selected by setting bit 0 in PCM register
five to a 0. The settings for the various submodes of
DLL mode are described in the following paragraphs.
Divider DIV0 may be used with any of the DLL modes
to divide the input clock by an integer factor of 1 to 8
prior to implementation of the DLL process.
Delayed Clock
A delayed version of the input clock can be constructed
in DLL mode. The output clock can be delayed by
increments of 1/32 of the input clock period. Delay
mode is selected by setting register six, bits [5:4] to 10
or 11 for ExpressCLK output, and/or bits [7:6] to 10 for
system clock output. The delay value is entered in reg-
ister four. See register four programming details for
more information. Delay values are also shown in the
Note that when register six, bits [5:4] are set to 11, the
ExpressCLK
output is divided by an integer factor from
1 to 8 while the system clock cannot be divided. The
ExpressCLK
divider is provided so that the I/O clocking
provided by the ExpressCLK can operate slower than
the internal system clock. This allows for very fast inter-
nal processing while maintaining slower interface
speeds off-chip for improved noise and power perfor-
mance or to interoperate with slower devices in the
system. The divisor of the ExpressCLK frequency is
selected in register two. See the register two program-
ming details for more information.
1x Clock Duty-Cycle Adjustment
A duty-cycle adjusted replica of the input clock can be
constructed in DLL mode. The duty cycle can be
adjusted in 1/32 (3.125%) increments of the input clock
period. DLL 1x clock mode is selected by setting bit 4
of register five to a 1, and duty-cycle adjustment is
selected by setting register six, bits [5:4] to 01 for
ExpressCLK
output, and/or bits [7:6] to 01 for system
clock output. The duty-cycle percentage value is
entered in register four. See register four programming
details for more information. Duty cycle values are also
Table 27. DLL Mode Delay/1x Duty Cycle
Programming Values
Register 4 [7:0]
7 6 5 4 3 2 1 0
Delay
(CLK_IN/32)
Duty Cycle
(% of CLK_IN)
0 0 X X X 0 0 0
1
3.125
0 0 X X X 0 0 1
2
6.250
0 0 X X X 0 1 0
3
9.375
0 0 X X X 0 1 1
4
12.500
0 0 X X X 1 0 0
5
15.625
0 0 X X X 1 0 1
6
18.750
0 0 X X X 1 1 0
7
21.875
0 0 X X X 1 1 1
8
25.000
0 1 X X X 0 0 0
9
28.125
0 1 X X X 0 0 1
10
31.250
0 1 X X X 0 1 0
11
34.375
0 1 X X X 0 1 1
12
37.500
0 1 X X X 1 0 0
13
40.625
0 1 X X X 1 0 1
14
43.750
0 1 X X X 1 1 0
15
46.875
0 1 1 1 1 X X X
16
50.000
1 0 0 0 0 X X X
17
53.125
1 0 0 0 1 X X X
18
56.250
1 0 0 1 0 X X X
19
59.375
1 0 0 1 1 X X X
20
62.500
1 0 1 0 0 X X X
21
65.625
1 0 1 0 1 X X X
22
68.750
1 0 1 1 0 X X X
23
71.875
1 0 1 1 1 X X X
24
75.000
1 1 0 0 0 X X X
25
78.125
1 1 0 0 1 X X X
26
81.250
1 1 0 1 0 X X X
27
84.375
1 1 0 1 1 X X X
28
87.500
1 1 1 0 0 X X X
29
90.625
1 1 1 0 1 X X X
30
93.750
1 1 1 1 0 X X X
31
96.875