JPS6314247A - Scan path control system - Google Patents

Abstract

PURPOSE:To improve the reliability of scan paths with a small amount of hardware by providing a plural scan paths, registers, and a scan data buffer and outputting shift out data while selecting it. CONSTITUTION:In case of scan out, contents of scan paths 11 and 12 are shifted out bit by bit in response to a shift clock to output shift out data 111 and 121 to registers 23 and 24 when an address counter 22 is initialized. When 8 bits are inputted to registers 23 and 24, this input data is written in a scan data buffer 21 through a selecting circuit 25. After the write operation to the buffer 21 and the shift-out operation to paths 11 and 12 are completed, contents of the buffer 21 are outputted to a maintenance and diagnostic device 3. Thus, a data 121 of the path 12 is correctly read out even in case of trouble in the path 11, and the reliability of scan paths is improved with a small amount of hardware.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a control method for a scan canvas used in a data processing device.

[Conventional technology]

As is well known, scanvases are widely used in data processing devices and play a very important role. Typical functions that Scanvasse performs include: ■ device initial settings, ■ logout data collection in the event of device failure, ■ device diagnosis and testing, and ■ device debugging. It can be used.

Therefore, if the scan canvas breaks down, it will cause a great deal of trouble. In particular, the above ■ to read the internal state of the device
The scan canvas function common to , ■, and ■ is the most important.

Conventionally, a scan bus is constructed by connecting flip-flops in series, and data is bit-serially inputted from a scan-in data line provided at the input end of the flip-flop row, and a scan-in data line provided at the output end of the flip-flop row. Data is output bit serially from the scan-out data line.

[Problem that the invention seeks to solve]

The conventional scan canvas control method described above has a problem in that if a failure occurs during the scan canvas, all data after the failure point will be lost in the case of scan out. In other words, if a failure occurs in the area marked with an X in the scan canvas of FIG. 4, all data in the shaded area after that point will be lost.

[Failure to solve the problem]

The system of the present invention consists of a plurality of scan canvases each consisting of the same number of 70 flip-flops connected in series and shifting the data stored in the flip-flops in the order of the series connection in response to a clock; a scan canvas-compatible write register that holds and outputs data in bit parallel; a selection circuit that selects one of the write registers according to a predetermined rule; and a selection circuit that sequentially stores the data output from the selection circuit. It has a scan data buffer and a read register that holds data read from the scan data buffer and outputs it in bit series to the first scan canvas of the scan canvas group and in bit parallel to the outside. Scan-in data written to the scan data buffer from the outside is sequentially written to a group of scan canvases, and scan-out data read from each scan canvas to the scan data buffer is read out to the outside during scan out. do.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, 1 is a data processing device, which includes scan canvases 11 and 12. 2 is a scan canvas control device, and 3 is a maintenance diagnosis device for processing scan data.

In the scan canvas control device 2, 21 is a scan data buffer for holding scan-in data and scan-out data, and is capable of holding a plurality of words each consisting of, for example, 8 data bits. The scan data buffer 21 can be constructed from a conventional RAM.

22 is an address counter for instructing a word address to the scan data buffer 21, and has a function of incrementing whenever the scan data buffer 21 performs writing or reading.

23 and 24 are registers for temporarily holding data written to the scan data buffer 21, and have a function (only 23) of holding one word worth of data 31 sent from the maintenance diagnosis device 3; Scanvas 11.12
It has a function of shifting scan-out data 111 and 121 from 1 bit at a time to the shift-out area and holding 1 word from 10,000. The register 23 is a type of register capable of parallel input/output and serial input.

The selection circuit 25 is for selecting one of the registers 23 and 24 and sending the write data to the scan data buffer 21.

26 is for holding one word of data read from the scan data buffer 21, and has a function for sending data in word units to the maintenance diagnosis device 3, and a function for scanning the scan data 261 one bit at a time. 11.1
This register is capable of parallel input/output and serial output, and has the function of sending data to the 2nd line.

Reference numeral 27 is a scan control circuit for controlling the scan operation and the scan-out operation, and has the function of supplying a shift clock, controlling the parallel input/output/serial input/output of the registers 23 and 26, and the selection operation of the selection circuit 25. included.

Next, the scan-in operation will be explained first.

After the address counter 22 is initialized, the data to be scanned in from the maintenance diagnosis device 3 is set in the register 23 in units of one word. The contents of the register 23 are written to the address of the scan data buffer 21 indicated by the address counter 22, and the address counter 22 is incremented.

Once all the scan-in data has been set in this way, a shift-in operation for the scan canvases 11 and 12 is then executed. The address counter 22 is initialized again, and the contents of the scan data buffer 21 are read word by word to the register 26, and the address counter 22 is incremented. The data read into the register 26 is sequentially sent one bit at a time to the input terminal of the scan canvas 12 as shift-in data.

Each time a shift clock is supplied to the scan canvas 11 and 12, the shift-in data is shifted one bit at a time.
New shift-in data is read out from the scan data buffer 21 to the register 26 every time a bit is shifted.

Next, the scan-out operation will be explained.

When the address counter 22 is initialized, its contents are changed to 1 from the shift path 11.12 in response to the shift clock.
The bits are shifted bit by bit, and shift-out data 111 and 121 are output from the beginning of the scan canvas 11 and the beginning of the scan canvas 12, respectively. Shift out data 1
11 and 121 are serially input to registers 23 and 24, respectively.

When the scan out data of 8 bits t appears in the registers 23 and 24, writing is performed to the scan data buffer 21 via the selection circuit 25. The write word is specified by the address counter 22, but the register 2
The write word designations of register 3 and register 24 are controlled differently. Various methods can be considered for this word addressing method. For example, it is conceivable to store the contents of the scan canvas 12 in the even addresses for the register 23, the contents of the system canvas 11 in the even addresses, and the odd addresses for the register 24, that is, the contents of the scan canvas 12 in the odd addresses.

Each time the contents of the registers 23 and 24 are written to the scan data buffer, the address counter 22 increments and moves to the next word.

In this way, the contents of the scan data buffer 21 are sent to the maintenance diagnosis device 3 after the data write operation to the scan data buffer 21 for every 8 bits (1 word) and the shift out operation to the scan canvas 11.12 are completed. and read out. That is, the address counter 22 is initialized again, the contents of the scan data buffer 21 are read out to the register 26 by one word, and then sent to the maintenance diagnosis device 3. The address counter 22 is incremented every time it is read. As explained above, l
Data is sequentially read word by word.

In the scan-out operation controlled in this manner, a case where the scan canvas is out of order will be described.

As shown in Figure 3, even if the same location as in Figure 4 fails,
Since the contents of the scan canvas after the second scan-out data line can be read correctly, less data is lost than in the past.

Further, FIG. 3 shows an embodiment in which the number of scan-out data lines is three, and in this case, the amount of lost scan data can be reduced compared to that in FIG. 2. In other words, the more scan-out data lines there are, the less data is lost due to failure. The number of scan-out data lines can be selected at the time of application since it is related to the investment and effect of gold material quantity and reliability.

Furthermore, if the failure of the scan canvas occurs near the end, the amount of data lost even in the conventional method is small, so the present invention is more effective against failures near the beginning of the scan canvas.

〔Effect of the invention〕

As explained above, the present invention has the effect that a scan line with improved reliability can be achieved with a smaller amount of metal than by providing a plurality of scan-out data lines and outputting them while selecting them. .

Furthermore, by employing the present scanvase method, it is possible to facilitate the search for the scancanse failure location, and to improve the scanout performance by performing scanout operations in parallel.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. 2 and 3 are diagrams explaining the present invention in detail, and FIG. 4 is a diagram explaining the conventional scan canvas method, respectively. ■...Data processing device, 2...Scanvas control device, 3...Maintenance diagnosis device, 10,
11,12゜28.29.30...Scan canvas, 21...Scan data buffer, 22.
...Address counter, 23.24.26...
...Register, 25...Selection circuit, 27...
...Scanvas control circuit. Finally, agent: Susumu Uchihara, patent attorney.・Kono'' Figure 2 $ 3 Concave grass 4 Figure

Claims (1)

[Scope of Claims] A plurality of scanspaces, each consisting of the same number of series-connected flip-flops, for shifting data stored in the flip-flops in the order of the series connection in response to a clock; a write register compatible with the scan canvas that holds and outputs data in bit parallel; a selection circuit that selects one of the write registers according to a predetermined rule; and a selection circuit that sequentially outputs data from the selection circuit. and a read register for holding data read from the scan data buffer and outputting it to the first scan canvas in bit series and in bit parallel to the outside. During scan-in, the scan-in data written from the outside to the scan data buffer is sequentially written to the scan canvas group, and during scan-out, the scan-out data read from each of the scan canvases to the scan data buffer is written. A scan canvas control method characterized by readout to the outside.