Electronic digital logic circuitry – Significant integrated structure – layout – or layout...
Reexamination Certificate
2001-01-16
2003-06-24
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Significant integrated structure, layout, or layout...
C326S021000, C327S403000, C327S261000, C327S170000, C327S165000, C375S285000, C375S346000
Reexamination Certificate
active
06583649
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to signal transmission apparatus for transmitting a plurality of rectangular wave signals whose rising or falling edges may occur substantially simultaneously, and to a data processing apparatus including such a signal transmission apparatus.
2. Description of the Related Art
Currently, data processing apparatuses for performing various data processing are utilized in many fields. Such data processing apparatuses are configured in varying forms depending on required performance or use environments. For example, when a data processing apparatus comprising ICs (Integrated Circuit) is used in a particular application, the data processing apparatus may incorporate a unique circuit apparatus as an ASIC (Application Specific IC).
Such ICs are typically configured by digital circuits, but may includes analog circuits. In this case, since the digital circuits perform digital processing and the analog circuits perform analog processing, it is possible to utilize the advantages of both digital operation and analog operation.
However, when a digital circuit produces rectangular wave signals as digital data, rising or falling edges may simultaneously occur in a plurality of rectangular wave signals. Such simultaneous occurrence of rising or falling edges in a plurality of rectangular wave signals produces much noise which is likely to affect analog circuits.
An apparatus which intends to solve such a problem is disclosed, for example in Japanese Patent Laid-open Publication No. 9-23148.
FIG. 1
shows the configuration of a conventional signal transmission apparatus disclosed in the gazette.
This conventional signal transmission apparatus
100
comprises, for example, five signal transmission paths
101
to
105
as a plurality of signal transmitting means. Each of signal transmission paths
101
to
105
respectively transmit a rectangular wave signal. The rising and falling edges of these signals may occur substantially simultaneously.
Signal transmission path
101
consists of one simple signal wire, while signal transmission paths
102
to
105
are each connected to delay circuits
117
. Signals which are delayed by delay circuits
117
for a predetermined time period are supplied to one terminal of respective selectors
107
to
110
and to four delay circuits
112
to
115
with differing delay times. Signals which are delayed by delay circuits
112
to
115
are supplied to the other terminal of respective selectors
107
to
110
.
Each of selectors
107
to
110
selects and outputs either the signal from delay circuit
117
or the signal from the associated delay circuit. Signal transmission paths
101
to
105
are also connected near their input terminals to switching control circuit
116
which in turn is connected to control terminals of selectors
107
to
110
.
Switching control circuit
116
counts rectangular wave signals whose rising edges and falling edges occur simultaneously of five rectangular wave signals transmitted through signal transmission paths
101
to
105
, and performs control to cause selectors
107
to
110
to select the signal from the associated delay circuit if the count exceeds a predetermined threshold value.
Delay circuits
117
having the same delay time inserted in respective signal transmission paths
102
to
105
serve the delay rectangular wave signal for a time period required for the operations of switching control circuit
116
and selectors
107
to
110
.
In the aforementioned conventional signal transmission apparatus
100
, signal transmission paths
101
to
105
each transmit a rectangular wave signal. In the transmission, signal transmission path
101
transmits a rectangular wave signal without delay, while signal transmission paths
102
to
105
transmit rectangular wave signals after the signals are delayed as required.
Next, the operation of conventional signal transmission apparatus
100
is described.
When a rectangular wave signal is transmitted through respective signal transmission paths
101
to
105
, switching control circuit
116
counts the number of the simultaneous occurrence of rising and falling edges in the signals. If the counted number is below the predetermined threshold value, then switching control circuit
116
causes selectors
107
to
110
to select the normal paths into which delay circuits
112
to
115
are not inserted. Thus, the rectangular wave signals are transmitted over signal transmission paths
102
to
105
without being delayed by delay circuits
112
to
115
.
However, if the number of the simultaneous occurrence of rising edges and falling edges in the five rectangular wave signals exceeds the predetermined threshold value, then switching control circuit
116
causes selectors
107
to
110
to select the paths into which delay circuits
112
to
115
are inserted.
Each of rectangular wave signals in signal transmission paths
102
to
105
is then delayed by delay circuits
112
to
115
for differing time periods. This causes rising edges and falling edges in the plurality of rectangular wave signals to occur in different timings, thereby preventing the occurrence of noise due to the simultaneous rising or falling of many signals.
Some digital circuits which output rectangular wave signals to the aforementioned signal transmission apparatus
100
and some digital circuits which receive rectangular wave signals from signal transmission apparatus
100
allow switch the setting of operational speeds.
However, in the aforementioned conventional signal transmission apparatus
100
, since delay circuits
117
are interposed in signal transmission paths
102
to
105
, each of rectangular wave signals is always delayed by delay circuit
117
for a predetermined time period regardless of the operations of switching control circuit
116
and each of selectors
107
to
110
. Furthermore, a delay time in delay circuit
117
is fixed, so that conventional signal transmission apparatus
100
cannot appropriately correspond to switching of the setting of the operational speed of a digital circuit.
For example, if the delay time in signal transmission apparatus
100
is designed to correspond to the low-speed operation of a digital circuit, the transmission of digital data will be uselessly delayed when the digital circuit is operated at high speed. On the other hand, if the delay time in signal transmission apparatus
100
is adapted to the high-speed operation of the digital circuit, the operation of delaying digital data will be late when the digital circuit is operated at low speed.
SUMMARY OF THE INVENTION
In view of the aforementioned problems, it is an object of the present invention to provide signal transmission method and apparatus which, when at least some of a plurality of rectangular wave signals are delayed for differing time periods to prevent the occurrence of noise, allows the setting of the delay time appropriately for the operational speed of a digital circuit.
The signal transmission apparatus according to the present invention comprises a plurality of signal transmitting means, a plurality of signal delaying means, and time varying means. With such a signal transmission apparatus, when the plurality of signal transmitting means each transmits a rectangular wave signal, rising or falling edges of these rectangular signals may occur substantially simultaneously, at least some of the plurality of rectangular wave signals transmitted by the plurality of signal transmitting means are delayed by the signal delaying means for differing time periods. Thus, the occurrence of noise due to the simultaneous rising or falling of many rectangular wave signals is prevented. In addition, the delay time in each of the plurality of signal delaying means is set by the time varying means based on the operational speed of a digital circuit which outputs digital data as rectangular wave signals.
In another aspect of the present invention, each of the plurality of signal delaying means comprises a predetermined number
NEC Corporation
Sughrue & Mion, PLLC
Tan Vibol
Tokar Michael
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