JPH1078861A - System for converting data using lookup table - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the use efficiency of the memory of a lookup table in which the range of a value to be converted is dynamically changed, and the wide value to be converted range is always used in an unnecessary way. SOLUTION: Two lookup tables 2 and 3 are serially connected in a hierarchical structure. The upper 16 bit of data to be converted 1 are connected with the address bus of the memory of the master lookup table 2, a flag part 22 of a flag for judging the data to be converted of a conversion data/slave table is provided at the 1 bit of the data, and a data part 21 in which the data to be converted of the conversion data/slave table are stored is provided at the residual 8 hit. The lower 8 bit of the data to be converted and the 8 bit of a data bus 41 of the master lookup table 2 are connected with the address bus of the memory of the slave lookup table 3, and conversion data are stored in a data part 31. When a flag = 0, the data of the master lookup table 2 are selected by a selector 6, and when a flag = 1, the data of the slave lookup table 3 are selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a data conversion system using a look-up table for performing high-speed data conversion.

[0002]

2. Description of the Related Art As a high-speed data conversion method, a conversion method using a lookup table is well known. A look-up table is a data in which a data value to be converted (data value to be converted) is input to an address value of the memory using a memory such as a ROM or a RAM, and a data value output from the memory is used as a conversion value. This is the method of performing the conversion.

Since the data conversion time is only the memory access time, data conversion can be performed at high speed. However, lookup tables are used in applications where the transformed value range is fixed and always requires a wide transformed value range (eg, when converting non-linear data to linear data). Often.

Therefore, if the look-up table is used as it is in a system in which the range of converted values is dynamically changed and a wide range of converted values is not always necessary, the efficiency of memory usage can be improved. Bad and not economic.

[0005]

For example, in a data conversion system in which the total number of data to be converted is 256 (8 bits) out of 1677216 (24 bits), a look-up table is used. When used, 1677216 words × 8 bits (1341
7728 bits) of memory is required, and the memory usage efficiency at that time is (= number of data searches (256) / memory capacity (1677216) * 100 = 0.0015%), which is inefficient and uneconomical.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the efficiency of use of a look-up table memory in which a range of converted values is dynamically changed and a wide range of converted values is not necessarily used as described above. It is to provide a method.

[0007]

The above object is achieved by providing a look-up table in a master / slave hierarchical structure.
The data structure of the master lookup table is composed of a data part and a flag part. This is achieved by providing a means for selecting a master / slave by a flag.

According to the above-described means, first, a search is performed in a certain bit range area of the data to be converted in the master lookup table, and the converted data whose conversion data is uniquely determined in the bit range is determined. The converted data for which the converted data cannot be determined is converted, and the converted data for which the converted data cannot be uniquely determined is converted using the slave lookup table.

The slave lookup table performs a search based on the data values in the bit range of the converted data not used in the master lookup table and the data values output from the master lookup table, and outputs the converted data.

The master look-up table has a function of outputting a flag which can determine whether the output data is converted data or a data value for searching the slave look-up table. Has a function of selecting a data value output from the master lookup table and a data value output from the slave lookup table.

As described above, the look-up table has a hierarchical structure of a master / slave and has a multistage cascade connection, so that the memory capacity of the look-up table can be reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention. The figure shows that, as an example, the total number of data to be converted is 16772
FIG. 10 is a configuration diagram of a look-up table in a data conversion system in which the number of data to be converted used at a certain time out of 16 (24 bits) is 256 (8 bits). Two lookup tables 2 and 3 are provided in a hierarchical connection.

The master lookup table 2 has 655
A memory having a capacity of 36 words × 9 bits (589824 bits) is used. The upper 16 bits 11 of the data to be converted 1 are connected to the address bus, and the conversion data / data to be converted in the slave table is determined for one bit of data. The flag section 22 of the flag has the remaining 8 bi
At t, a data section 21 for storing the converted data / converted data of the slave table is provided. Now, it is assumed that when the flag is “0”, the conversion data is stored, and when the flag is “1”, the conversion target data of the slave table is stored.

The slave lookup table 3 contains 6
A memory having a capacity of 5536 words × 8 bits (524288 bits) is used. The lower 8 bits 12 of the data to be converted and the 8 bits of the data bus 41 of the master lookup table 2 are connected to the address bus. Stores conversion data.

In this embodiment, the connection of the address buses of the master look-up table 2 and the slave look-up table 3 is set to the upper 16 bits and lower 8 bits, respectively.
Although the number of bits is set, there is no operational problem even if the connection is made with the lower 16 bits and the upper 8 bits.

Data bus 4 output from master look-up table 2 and slave look-up table 3
1 and 51 are connected to the selector 6.

When the converted data is input to the addresses of the lookup tables 2 and 3, the stored data is output from the lookup tables. When the flag is "0", the master lookup table 2 is output. When the flag is “1”, the data of the slave lookup table 3 is selected by the selector 6 and output as the conversion data 7.

By adopting such a configuration, the memory capacity can be 1114112 bits, which is about 1/10 (= 1114112b) as compared with the conventional method.
it / 13471728 bits), and the memory use efficiency is improved.

In the above embodiment, the selector is configured by hardware. However, if there is enough time for conversion, the selector can be realized by software processing of the MPU. FIG. 2 shows a flowchart when implemented by software.

Data conversion is started, and in step S1, the data value of the master lookup table 2 having the address of the upper 16 bits of the data to be converted is read. In step S2, the flag of the read data value is determined, and if the flag is "0", the data value of the master lookup table 2 is set as converted data in step S3. If the flag is "1" in the determination in step S2, an address is generated from the data value of the lower 8 bits of the converted data and the data value of the master lookup table 2 in step S4, and the data value of the slave lookup table 3 is read. The data value of the slave lookup table 3 is set as conversion data (S5).

[0022]

As described above, according to the present invention, in a data conversion system in which the range of values to be converted dynamically changes, the use efficiency of the memory of the look-up table can be remarkably improved, which is economically effective. Is big.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a process flowchart of another embodiment of the present invention.

[Explanation of symbols]

1 ... Data to be converted, 2 ... Memory of master lookup table, 3 ... Memory of slave lookup table,
41, 51: data bus, 6: selector, 7: converted data value.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kuki Nakajima 3-14-20 Higashinakano, Nakano-ku, Tokyo Inside Kokusai Electric Corporation

Claims (3)

[Claims] 1. A data conversion system for data in which a range of values to be converted dynamically changes, a plurality of lookup tables are provided in a multi-tiered connection in a hierarchical structure, and the master look-up table in the hierarchical structure has a master look-up table. A flag area is provided to indicate whether data output from the up-table is converted data or data to be converted in another slave lookup table, and the conversion data output from the master lookup table and the slave lookup table from the flag are provided. A data conversion system using a look-up table, further comprising means for selecting conversion data output from the data processing apparatus. 2. A data conversion system using a look-up table according to claim 1, wherein said data selection means is a selector for switching output conversion data according to a flag. 3. The data selection means according to claim 1, wherein when the flag is one, the data value of the master lookup table is used as the conversion data, and when the flag is the other, the data selection means uses the lower data value of the conversion data and the conversion data of the master lookup table. 2. A data conversion using a look-up table according to claim 1, wherein the data conversion is MPU software processing in which an address is generated, a data value of a slave lookup table is read, and a data value of the slave lookup table is converted data. system.