CN115801181A

CN115801181A - Digital quantity telemetering method based on double-cache structure

Info

Publication number: CN115801181A
Application number: CN202211261238.0A
Authority: CN
Inventors: 张雪; 韦宏春; 尹乐; 闫肖可; 贺小龙
Original assignee: Beijing Electromechanical Engineering Research Institute
Current assignee: Beijing Electromechanical Engineering Research Institute
Priority date: 2022-10-14
Filing date: 2022-10-14
Publication date: 2023-03-14
Anticipated expiration: 2042-10-14
Also published as: CN115801181B

Abstract

The invention provides a digital quantity telemetering method based on a double-cache structure, which comprises digital quantity feature extraction, cache structure design and data movement. The invention provides a double-buffer structure, which is characterized in that the traditional byte buffer is upgraded into a byte buffer and a whole frame buffer, digital quantity data used for frame coding of a telemetering acquisition device is read from the whole frame buffer, namely filling words are used for participating in frame coding only after the whole frame is read, and the problem of digital quantity telemetering error is successfully solved through the method.

Description

Digital quantity telemetering method based on double-cache structure

Technical Field

The invention belongs to the technical field of measurement and control, and particularly relates to a digital quantity telemetering method.

Background

The telemetering acquisition equipment is responsible for caching the received RS-422 digital quantity data, and framing the data with the received analog quantity data, the received sensing quantity data, the received switching quantity data and the like to form a PCM code stream and outputting the PCM code stream to the transmitter. When receiving the RS-422 digital data, in order to solve the problem of rate mismatch caused by the fact that the sending rate of the data source is far lower than the sending rate of the telemetry acquisition device, a cache structure is generally designed, and when the digital quantity in the cache is read empty, the telemetry acquisition device uses appointed filling words to replace the digital quantity for framing. The problem with this method is that when recovering the original RS422 digital data by telemetry, occasionally a filler word is inserted between an entire frame of digital data, resulting in a high telemetry error rate of the digital data, and it is correct to have a filler word between two entire frames and no filler word inside the entire frame.

Disclosure of Invention

The invention provides a digital quantity telemetering method based on a double-cache structure, which successfully solves the problem of digital quantity telemetering error.

A digital quantity telemetering method based on a double-cache structure comprises the following steps:

1) Digital quantity feature extraction

The digital quantity characteristics comprise a digital quantity frame length L and a whole frame sending interval T; the unit of the length of the digital frame is byte, and all data from the frame head to the frame tail are included; the time after the end of the nth frame is sent is recorded as T0, the time for sending the frame head of the (N + 1) th frame is recorded as T1, and the sending interval of the whole frame is T = T1-T0;

2) Cache structure design

Designing a double-cache structure of a first-level cache and a second-level cache, and determining the type, the width and the depth of a cache region; the first-level cache is a byte cache, and the second-level cache is a whole-frame cache;

3) Data migration

The step of moving the digital quantity data from the first-level cache to the second-level cache comprises the following steps:

a) Storage quantity: after the data acquisition equipment carries out bit-level receiving processing on the digital quantity data, 8-bit data is extracted and stored in a first-level cache;

b) Timing: when data is stored in a first-level cache, a time counter is assigned to be alpha x T, wherein a coefficient 0< alpha <1;

c) Waiting: if the first-level cache receives a new byte before the time counter is cleared, returning to the step b), otherwise, waiting for the time when the time counter is cleared;

d) Carrying: and at the moment of zero clearing of the counter, reading out the data in the first-level cache according to the original sequence and writing the data into the second-level cache.

Further, in 1), if the digital frame is lengthened, the maximum possible length is taken as a value of L; the entire frame transmission interval T is averaged by the data source.

Further, in 2), the type of the buffer area may be an RAM or FIFO type, the width of the buffer area is set to the bit width of the telemetry acquisition device during frame encoding, and the depth of the buffer area is set to be more than 2 times the length of the whole frame.

Further, in 3), the coefficient α =0.5 in the data transfer.

The invention designs a data moving process with strong fluctuation compatibility by designing a double-cache structure of byte cache and whole frame cache, solves the problem of digital quantity telemetering error caused by mismatching of digital quantity sending rate and telemetering coding and decoding rate, and realizes reliable receiving telemetering of digital quantity.

Drawings

FIG. 1 is a flow chart of a digital telemetry method.

FIG. 2 is a flow chart of a data moving method.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

In order to solve the problem of digital telemetering error, the invention provides a double-cache structure, the traditional byte cache is upgraded into byte cache and whole frame cache, digital data used for frame encoding of telemetering acquisition equipment is read from a whole frame cache region, namely filling words are used for frame encoding only after the whole frame is read, and the problem of digital telemetering error is successfully solved by the method.

1. Design idea

The design of the 'double-buffer' digital quantity receiving structure is generally divided into 3 steps:

a) Extracting digital quantity features;

b) Designing a cache structure;

c) And designing a data moving method.

The flow chart of the digital telemetry method is shown in figure 1.

2. Digital quantity feature extraction

The digital quantity characteristics mainly include two:

a) Digital frame length L: the unit of the length of the digital quantity frame is a byte, all data from the frame head to the frame tail are included, if the sending rule of the data chain is 1-bit start bit, 8-bit data bit, 1-bit stop bit and 1-bit check bit, the byte only has 8-bit data bit. If the frame is longer, the maximum possible length of the frame is taken as the value of L.

b) Whole frame transmission interval T: the time after the end of the nth frame is sent is denoted as T0, and the time for the header of the (N + 1) th frame to be sent is denoted as T1, so that the sending interval of the whole frame T = T1-T0, and the value is generally provided by the data source as an average value.

3. Cache structure design

The key to the design of the "double cache" structure is to determine the type, width and depth of the cache region. The type of the buffer area can be selected from RAM and FIFO, the width of the buffer area is set as the bit width when the telemetering acquisition equipment frames, and the depth of the buffer area is set to be more than 2 times of the length of the whole frame, depending on chip resources.

4. Data migration method design

The data transfer method specifies a rule for transferring digital quantity data from a first-level cache to a second-level cache, and is designed as follows:

a) Storage quantity: after the data acquisition equipment carries out bit-level receiving processing on the digital quantity data, 8-bit data are extracted and stored in a first-level cache;

b) Timing: when data is stored in the first level cache, the time counter is assigned to α × T, wherein the coefficient 0< α <1, α =0.5 is the optimal value.

The flow chart of the data moving method is shown in fig. 2.

5. Double cache architecture example

In the following example, the digital quantity to be telemetered is an RS-422 digital quantity, the frame length is 255 bytes, and the frame interval is 100ms on average.

The processing chip used in the telemetering acquisition equipment is an FPGA, the digital quantity cache overflow is avoided while the chip resource occupancy rate is considered, and the cache depth is designed to be about 2 times of the length of the whole frame. The first-level cache selects an RAM with the width of 8 bits and the depth of 512 bits, so that the requirement of storing 2 whole frames can be met; the second-level buffer is FIFO, the width is 8bit, the depth is 512, and the requirement of storing 2 whole frames can be met.

6. The characteristics of the invention

1) Designing a digital quantity receiving flow, aiming at different digital quantity remote measurement requirements, converting a byte cache into a byte cache and a whole frame cache through a digital quantity feature extraction step 1, a double-cache structure design step 2 and a data moving method design step 3, reading the digital quantity from the whole frame cache to participate in editing, and thus realizing that no filling word exists in the whole frame digital quantity and a filling word exists between two frames of digital quantity and effectively solving the problem of digital quantity remote measurement errors.

2) The data moving flow and the timer value are designed, and the design of the coefficient of 0.5 ensures that the method has stronger compatibility with the fluctuation of the whole frame interval, and can avoid the digital quantity telemetering error caused by the negative fluctuation of the frame interval.

The above embodiments are only for explaining and explaining the technical solution of the present invention, but should not be construed as limiting the scope of the claims. It should be clear to those skilled in the art that any simple modification or replacement based on the technical solution of the present invention may be adopted to obtain a new technical solution, which falls within the scope of the present invention.

Claims

1. A digital quantity telemetering method based on a double-cache structure is characterized by comprising the following steps:

1) Digital quantity feature extraction

2) Cache structure design

Designing a double-cache structure of a first-level cache and a second-level cache, and determining the type, the width and the depth of a cache region; the first-level cache is a byte cache, and the second-level cache is a whole frame cache;

3) Data migration

2. The digital telemetering method based on a double-cache structure according to claim 1, wherein 1) if the digital frame is lengthened, the maximum possible length is taken as the value of L; the entire frame transmission interval T is averaged by the data source.

3. The digital quantity telemetry method based on the double-buffer structure as claimed in claim 1, wherein in 2), the type of the buffer area can be selected from RAM or FIFO type, the width of the buffer area is set as the bit width when the telemetry acquisition device frames, and the depth of the buffer area is set to be more than 2 times of the length of the whole frame.

4. The digital quantity telemetry method based on the double-buffer structure as claimed in claim 1, wherein in 3), in data movement, the coefficient α =0.5.