Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Clock or pulse waveform generating
Reexamination Certificate
1999-11-10
2002-05-28
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Clock or pulse waveform generating
C327S293000, C327S564000
Reexamination Certificate
active
06396323
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor integrated circuit device and relates in particular to a semiconductor integrated circuit device having a high speed clock distribution network. This invention further relates to a technology capable of a high speed clock distribution network that efficiently utilizes design resources of independently designed semiconductor circuits.
2. Description of Related Art
FIG. 2
shows an example of a semiconductor integrated circuit device utilizing a high speed clock distribution network of the prior art. In the figure, the reference numeral
101
denotes a phase locked loop (PLL),
102
is a clock distribution line and
103
is a clock buffer. Reference numeral
120
denotes an input clock which is multiplied (increased) N times by the PLL
101
and output frequency to
102
as a multiplied (increased) by N times. The clock pulse multiplied by PLL
101
is amplified in
103
and distributed to each latch (latch and flip-flops are different from each other in the strict sense of the word, however here both latch and flip-flops are represented by the word “latch”) with an equivalent delay. Technical features assuring an equal-length wiring are utilized in order to achieve an equivalent distributed delay.
Once of the distributed clocks
104
is input to the PLL
101
and the PLL
101
functions to obtain an identical phase for the clocks
104
and
120
.
FIG. 3
shows the clock distribution network for the semiconductor integrated circuit device of
FIG. 2
when added with a macro
130
a
and
130
b
. A macro is a separately designed circuit that satisfies specifications for circuits other than the macro (hereafter referred to as mother circuits) as well as interface specifications between macro and mother circuit. As long as these interface specifications are satisfied, the macro can change the mother circuit in various ways.
As one example, the DRAM macro has a memory function to store information by means of capacitance in a circuit described in the 1998 IEEE International Solid-State Circuit Conference Digest of Technical Papers, pp. 72-73.
These macro circuits are sometimes designed as separate items by different designers. One designer may specialize in DRAM macro design while another may specialize in coprocessor macro design. A circuit can then be systematically assembled by combining the macros obtained from these different sources. This method allows utilizing existing macros to design system-level integration devices with high additional value.
In the macro, software IP is used to show design data at the circuit level, and hardware IP is data listing the physical structure of the semiconductor integrated circuit device such as the layout. Hardware IP is more appropriate when high speed operation is required, because performance cannot otherwise be guaranteed when redrafting the physical layout of the circuit.
The clocks distributed to the mother circuit latches are also supplied at an identical phase to the latches in the circuits
121
and
122
. The respective macros
130
a
and
130
b
distribute the clock pulses input from
121
and
122
to the latches within each macro at an equivalent delay by utilizing the clock buffers
133
a
and
133
b
within each macro.
The clock distribution in the semiconductor integrated circuit device of
FIG. 3
containing the macros is at a phase identical to the clock phase of
121
and
122
and the latch phase within each mother circuit. However, a delay time Tm is required from
121
and
122
to the input of the clocks to the latches within each macro so that a phase difference (skew) equivalent to the Tm, occurs between the latches within the mother circuit and the latches within the macros.
Further, the Tm within each macro is different so that skew also occurs between macros. This Tm tends to become large when using large scale macros (also called megacells) and the clock skew increases in the semiconductor integrated circuit device using these macros.
In the semiconductor integrated circuit devices of the prior art containing these macros, skew occurs between the clock pulses supplied to the latches within the mother circuit and the clock pulses supplied to the latches within the macro. These clock skews interfere with the high frequency function of the semiconductor integrated circuit device clock frequency so that the semiconductor integrated circuit device cannot be operated at high speed.
A proper delay time for the clock distribution network, from the clock buffer
103
to
121
or
122
calculated during the macro design stage, that takes the Tm into account will resolve this problem but has the drawback that macrocell design cannot be performed independently of mother circuit design.
SUMMARY OF THE INVENTION
In order to resolve the above mentioned problems, this invention has a clock generator to supply clock signals, a plurality of first controlled circuits supplied by the clock pulses from the clock generator and a phase adjuster for these clock signals, a second controlled circuit supplied by the clock signal that passed through the clock signal phase adjuster, and configured so that the clock phase input to this clock signal phase adjuster and first controlled circuit are an identical phase.
The number of first controlled circuits supplied at this time by clock pulses from the clock generator is typically larger than the number of clock signal phase adjuster (circuits).
This invention in this case, is characterized in having a clock generator to supply clock signals, a plurality of first controlled circuits supplied by the clock pulses from the clock generator and a phase adjuster for these clock signals, a second controlled circuit supplied by the clock signal that passed through the clock signal phase adjuster, and further characterized in that the number of the plurality of first controlled circuits supplied by clocks from the clock generator is larger than the number of clock signal phase control circuits.
To restate, this invention is characterized in that the percentage shared by first control circuits from among the fan-out of the clock generator is larger than the percentage of clock signal phase control circuits.
A phase adjusting means contains a phase frequency detector to compare the frequencies input with the first clock and the second clock, and is configured to output the three clock signals controlled by the output of the phase frequency detector.
In a more detailed description, the semiconductor integrated circuit device of this invention has a first clock processing means to input a first clock and a second clock and generate a third clock, a second clock processing means to input a third clock and a fourth clock and generate a fifth clock, and a first latch group and a second latch group comprised of at least one latch, wherein the second clock is generated from the third clock by way of a buffer, the frequency of the second and third clocks are identical, the first clock processing means generates the third clock so that the first and second clocks will have an identical phase and frequency, a fourth clock is generated by way of a buffer from the fifth clock, the frequency of the fourth and fifth clocks are identical, the second clock processing means generates a fifth clock so that the third and fourth clocks will have an identical phase and identical frequency, the third clock is supplied by way of a buffer to the first latch group, the fifth clock is supplied by way of a buffer to the second latch group, and the first latch group and the second latch group operate at an identical phase.
Phrases such as “identical phase, identical frequency” as related in these specifications, allow for an error of an extent that can be ignored without hindrance to actual operation and can be tolerated in terms of performance demanded of the circuit.
The first clock processing means of this invention as described in a more detailed example, consists of a phase frequency detector to input a first clock and a second clock
Luu An T.
Wells Kenneth B.
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