KR20030018999A - Apparatus and method for determining stuff time to generate VC pointer of SDH - Google Patents

Abstract

PURPOSE: A stuff time deciding device for generating a VC(Virtual Container) pointer of SDH(Synchronous Digital Hierarchy) and a method thereof are provided to decide a stuff time when reading and writing VC data of SDH in a memory element, so as to prevent overflow or underflow of the memory element and maintain an appropriate level. CONSTITUTION: A subtracter(411) performs a subtraction operation between a write pointer inputted from a write pointer generator and a read pointer applied from a read pointer generator, for comparison. A positive stuff decider(412) receives an operated result of the subtracter(411) to decide positive stuff. A negative stuff decider(413) receives the operated result of the subtracter(411) to decide negative stuff. A stuff output unit(412) receives outputs of the positive and negative stuff deciders(412,413) and temporarily stores the received outputs, to output positive stuff action or negative stuff action according to read clock outputted in an 'A' block. In the stuff output unit(412), a positive stuff output part includes flip flop-1(414) and a flip flop-2(415) storing outputs of the positive stuff decider(412) for outputting in accordance with the read clock. The first AND gate(418) performs an AND operation for outputs of each flip flop(414,415) to output the positive stuff action. A negative stuff output part includes flip flop-3(416) and a flip flop-4(417) storing outputs of the negative stuff decider(413) for outputting in accordance with the read clock. And the second AND gate(419) performs an AND operation for outputs of each flip flop(416,417) to output the negative stuff action.

Description

Stuff Time Determination Device and Method for Generating Virtual Box Pointer of Synchronous Digital Layer {Apparatus and method for determining stuff time to generate VC pointer of SDH}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the generation of a virtual container (or VC) pointer of a synchronous digital hierarchy (SDH), and more particularly to a storage device when writing / reading VC data of an SDH to a storage device. The present invention relates to a stuff time determining apparatus and a method for generating a VC pointer of the SDH for determining the stuff time so as to prevent overflow or underflow and maintain a proper level.

Recent synchronous transmission systems use a multiplexing scheme according to the SDH standard of the International Telecommunication Union-Telecommunication standardization section (ITU-T). The multiplexing method according to SDH facilitates circuit branching, combining, and circuit distribution functions, and provides various OAM & P (Operation, Administration, Maintenance and Provisioning) functions to quickly monitor and maintain performances between transmission stations and signal paths. .

The SDH system generates the STM-1 signal by accepting the input signals, mapping them by the virtual box VC, and processing and multiplexing the hierarchy unit (TU) pointer. The STM-1 signal is 155Mbps, which is multiplexed to produce STM-N (N = 1, 4, 16, 64 ...) signals. In this case, when the input signal is synchronized, the interleaved multiplexed signal is simply interleaved without going through a synchronization process.

In the multiplexing process, a stuffing bit is used to match the speed of the input signal with the speed of the system clock. In SDH the stuff bits are inserted in fixed positions on the payload. For example, when three AU-3 signals are multiplexed by AUG, two stuff bits are put in the same position for each AU-3.

Fig. 1 is a block diagram of a stuff determining device using a general pointer, Fig. 2 is a detailed view of block A in a conventional stuff determining device, and Fig. 3 is a signal timing diagram of the device according to Fig. 2.

According to FIG. 1, the stuff determining device includes a memory device 130, an A block 110 for reading the memory device 130, and a B block 120 for writing to the memory device 130.

The A block 110 reads VC data from the memory device 130 by providing a read address, a read clock, and a read enable signal. In such a scheme, the B block 120 provides data Write VC, a write address, a write clock, and a write enable signal to be written to the memory device 130.

The read pointer generator 140 receives a read clock and a read enable signal from the A block 110 to generate a read pointer. The write pointer generator 150 receives a write clock and a write enable signal from the B block 120 to generate a write pointer.

In this case, the memory device 130 stores the input VC data at a location designated by a write address.

According to FIG. 2, the A block 110 includes a subtractor 111, a positive stuffing determiner 112, a negative stuffing determiner 113, and two flip-flops 114 and 115.

The read pointer and the write pointer values applied to the A block 110 are subtracted by the subtractor 111, and the result of the subtraction is the positive stuffing determining unit 112 and the negative stuffing determining unit 113. Is applied to determine positive stuffing and negative stuffing.

Positive stuffing and negative stuffing are stored in flip-flops 114 and 115 and output as positive stuffing action and negative stuffing action, respectively. As such, the stuff time is determined during the multiplexing process of the SDH.

However, according to the related art, when the write clock and the read clock are not synchronized as shown in FIG. 3, the value in the transition period between the write pointer and the read pointer is read. Taking and subtracting gives a problem that it is impossible to determine positive or negative stuff.

SUMMARY OF THE INVENTION The present invention was created to solve the above conventional problems, and an object of the present invention is to determine the stuff time when writing / reading VC data of SDH to a memory device, thereby reducing the overflow or underflow of the memory device. It is to provide a stuff time determination device for generating VC pointer of SDH that prevents and maintains an appropriate level.

Another object of the present invention is to generate a positive stuff and a negative stuff according to the difference between a write pointer and a read pointer value, and read and then multiply by a read clock to generate a stuff time for generating a VC pointer of the SDH to determine whether it is positive or negative stuff. To provide a decision method.

1 is a block diagram of a stuff determining device using a general pointer,

Figure 2 is a detailed view of the A block in the conventional stuff determination device,

3 is a signal timing diagram of the apparatus according to FIG.

4 is a block diagram of a stuff time determining apparatus for generating a VC pointer of an SDH according to an embodiment of the present invention;

5 is a configuration example of a memory device according to an embodiment of the present invention;

6 is a signal timing diagram according to an embodiment of the present invention;

7 is a flowchart illustrating a stuff time determining method for generating a VC pointer of an SDH according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

411: subtractor 412: positive stuff determiner

413: negative stuff determining unit 414, 415, 416, 417: flip-flop

418, 419: AND gate 420: Stuff output stage

In order to achieve the above object, a stuff time determining apparatus for generating a VC pointer of an SDH of the present invention includes: a comparison unit for comparing two input signals; A positive stuff determiner for determining positive stuff by receiving a comparison result from the comparator; A negative stuff determining unit for determining a negative stuff by receiving a comparison result of the comparing unit; It is characterized in that it comprises a stuff output stage for receiving the output of the positive stuff determiner and the negative stuff determiner and output according to the set read clock.

Here, the comparator may be a subtractor for subtracting two input signals.

The stuff output stage stores the output of the positive stuff decision unit and performs a logical AND operation on the positive stuff output unit having a plurality of flip flops for outputting according to the read clock, and the output of each flip flop unit of the positive stuff output unit as a positive stuff action. Negative stuff output unit having a plurality of flip-flops for storing the first AND gate for output, the output of the negative stuff determiner, and outputs the output according to the read clock, the output of each flip-flop of the negative stuff output unit And a second AND gate for outputting as a negative stuff action.

A stuff time determining method for generating a VC pointer of the SDH of the present invention for achieving the above object comprises the steps of: calculating a difference between an input write pointer and a read pointer value; Outputting a first positive stuff and a first negative stuff simultaneously from a positive stuff determiner and a negative stuff determiner when it is determined that a difference between the write pointer and the read pointer value has a value set in a specific phase of a read clock; ; Outputting a second positive stuff or a second negative stuff according to a difference between the write pointer and the read pointer value calculated on a reverse phase of a specific phase of the read clock, and outputting the outputted second positive stuff or second negative stuff And a logical AND operation with the first positive stuff and the first negative stuff to determine whether it is a positive stuff or a negative stuff.

Here, the read pointer and the write pointer indicate the pointer position of the memory device, and the memory device is allocated a certain number of areas for the positive stuff and the negative stuff time, and puts a guard time area between the positive stuff and the negative stuff time. Do not overlap.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

4 is a block diagram of a stuff time determining apparatus for generating a VC pointer of an SDH according to an embodiment of the present invention, FIG. 5 is a configuration example of a memory device according to an embodiment of the present invention, and FIG. 6 is an embodiment of the present invention. A signal timing diagram according to an example.

This embodiment is applied to the stuff determining device using the pointer shown in FIG. 1, and the following reference numerals of FIG.

According to FIG. 4, the stuff time determining apparatus compares each other by subtracting a write pointer input from the write pointer generator 140 and a read pointer applied from the read pointer generator 150. 411), a positive stuff determining unit 412 for determining the positive stuff by receiving the operation result of the subtractor 411, and a negative stuff determining unit for determining the negative stuff by receiving the operation result of the subtractor 411 ( 413, the positive stuff decision unit 412 and the negative stuff decision unit 413 receive the output temporarily stored in the positive stuff action (positive stuff action) according to the read clock (readclk) output from the A block 110 Or a stuff output stage 420 for outputting as a negative stuff action.

The stuff output stage 420 includes a positive stuff output unit and a positive stuff output unit having a flip-flop 1 414 and a flip-flop 2 415 that store the output of the positive stuff determiner 412 and output the stored data according to a read clock. The output of the first AND gate 418 and the negative stuff determiner are stored by performing a logical AND operation on the outputs of the flip-flops 414 and 415 of the stuff output unit and outputting them as a positive stuff action. a negative stuff action by performing an AND operation on the output of each of the negative stuff output unit having the flip-flop 3 (416) and the flip-flop 4 (417), and the output of each flip-flop (416, 417) of the negative stuff output unit. and a second AND gate 419 which outputs as a negative stuff action.

According to FIG. 5, the memory device 130 writes the VC unit data read from the B block 120 at the pointer positions indicated by the read pointer and the write pointer, and the A block 110 reads the VC unit data. To help.

In order to prevent memory overflow or underflow from occurring while determining the stuffing time in the memory device 130, the memory device 130 is divided into a plurality of areas. Separate areas of the memory device 130 are allocated to the positive stuff and the negative stuff by a predetermined number. In this case, in order to prevent overlap between the positive stuff and the negative stuff, the guard time is further allocated to configure each area of the memory device 130.

For example, the memory device 130 is divided into eight regions suitable for one-byte processing, where 0 to 2 are allocated for positive stuff, 3 to 4 for guard time, and 5 to 7 are negative. Can be allocated for stuff.

Thus, as shown in FIG. 6, when the difference between the value of the write pointer and the read pointer becomes 7 (= '111') in the polling edge of the read clock readclk, the positive stuff determiner 412 The negative stuff decision unit 413 generates both the positive stuff and the negative stuff.

The result is a logical AND operation with the value at the next rising edge of the read clock (clcl) to determine the positive or negative stuff.

An embodiment of the stuff time determination method of the present invention will be described below.

7 is a flowchart illustrating a stuff time determining method for generating a VC pointer of an SDH according to an embodiment of the present invention.

Referring to FIG. 7, a write pointer input from the write pointer generator 150 and a read pointer value input from the read pointer generator 140 to determine the stuff time for generating the VC pointer of the SDH. Compute the difference (S610).

Subsequently, it is determined whether the difference between the write pointer and the read pointer value has a value set in a specific phase of the read clock readclk inputted from the A block 110. At this time, the specific phase is to be the falling edge of the read clock readclk, and the value determined in this phase is set to 7 (= '111'), which is the most significant bit of the memory device 130. In this case, it is determined whether the difference between the value of the write pointer and the read pointer is 7 in the polling edge of the read clock readclk (S620).

If it is determined in step S620 that the condition is satisfied, the positive stuff determining unit 412 and the negative stuff determining unit 413 simultaneously generate the possibility of positive stuff and negative stuff. This is achieved by simultaneously outputting the first positive stuff and the first negative stuff (S630).

In operation S630, the second positive stuff or the second negative stuff is output according to the difference between the write pointer and the read pointer value at the next rising edge of the read clock readclk (S640).

Subsequently, in step S640, the second positive stuff or the second negative stuff is logically ORed to the first positive stuff and the first negative stuff, respectively, to determine whether the positive stuff or the negative stuff is present (S650).

For example, the first positive stuff is temporarily stored in flip-flop 1 414, the second positive stuff is temporarily stored in flip-flop 2 415, and then the first AND at the rising edge of the read clock readclk. It is a system that is output to the gate 418 and is ANDed and the positive stuff action is output as a result of this AND.

The AND operation on the first negative stuff and the second negative stuff consists of a system corresponding to the AND operation on the illustrated first positive stuff and the second positive stuff.

The embodiments described above are within the scope of various changes, modifications, and equivalents of the present invention. Therefore, the present invention is not limited to the description of the examples.

According to the present invention, a stuff time determining apparatus for generating VC pointer of SDH and a method suitable for preventing overflow or underflow of a memory device when writing / reading VC unit data of SDH to a memory device are provided. This has the effect of being able to determine the time.

Therefore, the present invention has an advantage of preventing damage to the VC unit data stored and read in the memory device.

Claims (6)

A comparator for comparing two input signals; A positive stuff determiner for determining positive stuff by receiving a comparison result from the comparator; A negative stuff determining unit for determining a negative stuff by receiving a comparison result of the comparing unit; And a stuff output stage configured to receive and store the outputs of the positive stuff determiner and the negative stuff determiner and output the stored data according to a set read clock. The method of claim 1, wherein the comparison unit, A stuff time determining apparatus for generating a virtual box pointer of a synchronous digital hierarchy, comprising: a subtractor for subtracting two input signals. The stuff output terminal of claim 1 or 2, A positive stuff output unit having a plurality of flip-flops for storing the output of the positive stuff determining unit and outputting the output according to the read clock; A first AND gate for performing an AND operation on the output of each flip-flop of the positive stuff output unit and outputting the result as a positive stuff action; A negative stuff output unit having a plurality of flip-flops for storing the output of the negative stuff determining unit and outputting the negative stuff determining unit according to the read clock; And a second AND gate for performing an AND operation on the output of each flip-flop of the negative stuff output unit to output the negative stuff action as a negative stuff action. (A) calculating a difference between an input write pointer and a read pointer value; When it is determined that the difference between the write pointer and the read pointer value has a value set at a specific phase of a read clock, the positive stuff determiner and the negative stuff determiner simultaneously output the first positive stuff and the first negative stuff (b). ) Step; Outputting a second positive stuff or a second negative stuff according to a difference between the write pointer and the read pointer value calculated on a reverse phase of a specific phase of the read clock, and outputting the outputted second positive stuff or second negative stuff 1. The method of claim 1, further comprising: (c) determining whether the positive stuff or the negative stuff is performed by performing an AND operation on the positive stuff and the first negative stuff. The method of claim 4, wherein The read pointer and the write pointer indicate a pointer position of a memory device. The memory device is a virtual box of a synchronous digital hierarchy, characterized in that a specific number of areas are allocated to positive stuff and negative stuff time, and a guard time area for spare time is allocated between the positive stuff and negative stuff time. How to determine stuff time for pointer creation. The method of claim 5, wherein in step (b), The specific phase of the read clock is a falling edge, and the set value is a value of the uppermost region of the negative stuff time allocated to the memory device. A stuff time determination method for generating a virtual box pointer of a synchronous digital hierarchy. .