Electrical computers and digital processing systems: memory – Storage accessing and control – Hierarchical memories
Reexamination Certificate
1998-05-19
2001-09-04
Thai, Tuan V. (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Hierarchical memories
C711S100000, C711S154000
Reexamination Certificate
active
06286081
ABSTRACT:
TECHNICAL FIELD
This invention relates to digital electronic systems, and more particularly, to an apparatus and method for ensuring data coherency during sequential readings of portions of data even though such data changes with time.
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, a data generator
100
generates data having a plurality of portions. For example, the data generator
100
may be a counter or a register having a plurality of bits as data. For instance, referring to
FIG. 1
, a first portion
102
of the data includes a first 8-bit (byte) portion, a second portion
104
of the data includes a second 8-bit (byte) portion, a third portion
106
of the data includes a third 8-bit (byte) portion, and a fourth portion
108
of the data includes a fourth 8-bit (byte) portion. With many common types of the data generator
100
, such as a counter or a register, the data bits constantly change with time.
An electronic reading device which reads the 32-bit data from the data generator
100
in many cases cannot read all 32-bits of the data together at once. The electronic reading device may lack the data capacity necessary for reading 32-bits of the data together at once. In that case, the electronic reading device sequentially reads the data, at least one portion at a time. For example, referring to
FIG. 1
, the electronic reading device may have the data capacity for reading 8-bits at a time. In such an example, the electronic reading device may sequentially read the first 8-bit portion
102
, then the second 8-bit portion
104
, then the third 8-bit portion
106
, and then finally, the fourth 8-bit portion
108
. In this example, each 8-bit portion is read sequentially one portion at a time.
However, each bit of the 32-bits within the data generator
100
is updated with time. Thus, between the time the electronic reading device reads the first portion
102
and the time the electronic reading device reads any subsequent portion (i.e., the second portion
104
, the third portion
106
, or the fourth portion
108
), any bit within the 32-bit data may be changed. In that case, the four portions
102
,
104
,
106
, and
108
which are thus sequentially read do not represent the data of the data generator
100
.
In such a scenario, the four portions are deemed to be “incoherent.” Incoherent data is an inaccurate representation of the content of the data generator
100
. However, many electronic reading devices can only read data from the data generator
100
in a plurality of sequential portions rather than all of the bits at once. Thus, a mechanism for ensuring coherency among the portions of data sequentially read from the data generator
100
is desired.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to allow an electronic reading device to sequentially read portions of data bits at a time while ensuring coherency among such portions.
In a general aspect, the present invention ensures data coherency when data comprising a plurality of portions is read sequentially at least one portion at a time by a reading device, wherein the data changes with time. The present invention includes a data storage unit for storing the plurality of portions of the data having a prior status at a prior time point when the reading device begins to read at least one portion of the data at the prior time point. The present invention also includes a monitoring unit for determining whether the reading device is continuing to read the plurality of portions of the data having the prior status of the prior time point. In addition, the present invention further comprises a multiplexing unit, operatively coupled to the data storage unit, the reading device, and the monitoring unit, for transferring at least one portion of the data having the prior status from the data storage unit to the reading device when the reading device continues to read at least one portion of the data having the prior status of the prior time point.
The present invention may be used to particular advantage when the monitoring unit also determines when the reading device begins reading at least one portion of the data having a subsequent status at a subsequent time point. In that case, the multiplexing unit transfers to the electronic reading device at least one portion of the data having the subsequent status of the subsequent time point, and the data storage unit stores the plurality of portions of the data having the subsequent status of the subsequent time point.
In another aspect of the present invention, the monitoring unit monitors whether any portion of the plurality of portions of the data is read for a second time in determining that the reading device begins reading the data having the subsequent status.
These and other features and advantages of the present invention will be better understood by considering the following detailed description of the invention which is presented with the attached drawings.
REFERENCES:
patent: 4622631 (1986-11-01), Frank et al.
patent: 5251308 (1993-10-01), Frank et al.
patent: 5737750 (1998-04-01), Kumar et al.
patent: 5933850 (1999-08-01), Kumar et al.
patent: 6018791 (2000-01-01), Arimilli et al.
Advanced Micro Devices , Inc.
Choi Monica H.
Thai Tuan V.
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