JP3097005B2 - Data transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transfer apparatus for transferring serial data at a high speed through an optical fiber.

[0002]

2. Description of the Related Art In recent years, data transmission using an optical fiber has been widely used, but its waveform distortion is a problem.

[0003] A conventional data transfer apparatus for transferring serial data at high speed by using an optical fiber will be described below. In a conventional data transfer apparatus, transmission data is coded, and the laser light is luminance-modulated by the serial data and transmitted. A Manchester code is widely used as a code used in this case to eliminate fluctuations in DC components in waveform transmission and reduce data errors.

[0004]

In such a conventional data transfer apparatus, the reproducibility of the waveform is important, and the waveform depends on the light quantity of the light emitting section in the transmitting apparatus and the characteristics of the light receiving section in the receiving apparatus. However, if the waveform of the received signal is distorted and the time length of the high level or the low level is different from the predetermined transmission waveform, a clock as a reference for reading the transmission data may not be correctly extracted.
Therefore, the data transfer is performed by adjusting the light amount of the light emitting unit in the transmitting device and the threshold level of the light receiving unit in the receiving device or selecting a transfer frequency so that the receiving device can correctly extract the clock. However, since the light amount of the light emitting unit and the threshold level of the light receiving unit change depending on the fluctuation of the temperature and the power supply voltage, there is a problem that it is difficult to restrict the environment in which the apparatus is installed and to adjust the light amount.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a data transfer device capable of completely transmitting and receiving data without being affected by the light amount of a light emitting section or the characteristics of a light receiving element.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a data transfer apparatus for converting Manchester-coded serial data into an optical signal and transmitting / receiving the signal via an optical fiber. When a continuous "0" data of more than bits is transmitted before the transmission data body and the output signal is fixed to no signal for a period corresponding to at least 2 bits after the transmission data body, and there is no transmission data Is a transmitter that fixes and outputs an output signal as no signal, and a receiver measures the high-level time width of the first detected “0” data after a no-signal of 2 bits or more, and measures the high-level time width. Is longer than a predetermined time width, the data of the subsequent received signal is “1”.
From “0” to “0”, the fall of the reference clock extracted from the received signal is advanced, and the high-level time width of the first detected “0” data after the no-signal of 2 bits or more is equal to the predetermined level. If it is shorter than the time width, when the data of the subsequent received signal changes from “0” to “1”,
The data transfer device includes a waveform distortion correction device that hastens the fall of a reference clock extracted from a received signal.

[0007]

According to the present invention, in the above configuration, the transmitting apparatus transmits continuous "0" data of 2 bits or more before the transmission data main body, and a period corresponding to at least 2 bits after the transmission data main body as a space. If there is no data to be transmitted, the signal is fixed to no signal and no data is transmitted. Two-bit or more “0” data after this space is a reference signal for detecting waveform distortion.

The receiving device detects whether the waveform of the first two bits of "0" data is a predetermined waveform by the distortion correction device based on the high-level time length of the waveform, and determines that the high-level time length is the predetermined time length. Transition of the Manchester electric signal by advancing the falling edge of the clock extracted and generated from the received signal at the transition point from "1" to "0" or "0" to "1" of the data in accordance with the longer or shorter time. Generates a clock corresponding to.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the data transfer apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. In the figure, a transmitting device 1
Converts parallel data into serial data of Manchester code, converts the electric signal into an optical signal, and outputs the optical signal to the optical fiber 3. The optical fiber 3 transfers the optical signal output from the transmitting device 1 to the receiving device 2. The receiving device 2 receives the optical signal of the optical fiber 3 and converts it into an electric signal. In this receiving operation, the pulse width of the Manchester code changes due to the transfer characteristic of the light receiving element in the receiving device 2,
This causes pulse width distortion and hinders normal restoration of transmission data. In the present invention, in order to correct the pulse width distortion, the receiving apparatus 2 estimates the manner of occurrence of the distortion by the distortion correcting apparatus 4 from the waveform patterns of the first two “0” data of the received signal. The distortion of a signal received thereafter is removed based on the waveform pattern, and the transmitted serial data is changed to parallel data.

First, generation of a data code transmitted by the transmission device 1 according to the present invention will be described. FIG. 2 is a block diagram illustrating a configuration of the transmission device 1. In this embodiment, a Manchester code that converts data “0” into “01” and converts data “1” into “10” is used, and a space where there is no signal fixes the signal to a low level. explain. In FIG. 2, the timing control unit 7
Controls Manchester encoding of transmission data at the timing of an external clock signal CLK2. The flip-flop 5 receives the LD signal, which is a write command signal output from the timing control unit 7, and sends a write enable signal, W, to an external device (not shown) that generates transmission data.
An E signal is output, and a WR signal as an external write signal is input to clear the WE signal. In the embodiment, the WE signal is set to the low level at the falling edge of the LD signal, and DATA, which is data to be transmitted to the external device, is written in the data temporary storage unit 8. The external device detects the low level of the WE signal, and writes the transmission data to the transmission data temporary storage unit 8 if the transmission data exists. When the writing is completed, the WR signal is set to the high level, and the WE signal is cleared by the WR signal and changes to the high level, and further writing of data is prohibited.

FIG. 3 is a timing chart showing the operation of coding the data stored in the transmission data storage section 8 in the above process. The data stored in the transmission data temporary storage unit 8 and the parity bit data generated by the parity bit generation circuit 9 are input to the shift register 10,
The data is sequentially output to the Manchester code generator 11 as serial data SD at the timing of the shift clock X0 obtained by dividing the clock CLK2 by two. The Manchester code generator 11 generates an MDC1 signal by an exclusive OR of the serial data SD output from the shift register 10 and the shift clock X0. The MDC1 signal has a Manchester code format. However, due to a timing shift between the serial data SD and the shift clock X0, FIG.
As shown in (1), spike-like noise such as a black portion of the MCD1 signal is mixed. To get rid of this,
The MCD1 signal is sampled by the flip-flop 12 at the rising edge of NCLK obtained by inverting the reference clock CLK2, thereby generating the Manchester electric signal MCD2 free from noise. The light emitting element 13 receives the Manchester electric signal MCD2 and outputs a Manchester optical signal MCD3 converted into an optical signal.

FIG. 4 is a schematic diagram showing a configuration of a frame which is one block of transmission data. In the figure, data A0 to A3 and D0 to DF are data to be transmitted, and P
1 and P2 are parity bits corresponding to the data D0 to DF. This parity bit is generated by the parity bit generation circuit 9. Prior to these data, 2
Bit "0" data is provided. This “0” data is realized by inserting 2-bit “0” data before the SD data output from the shift register 10. In the embodiment, the number of bits of a frame is 24 bits including "0" data. In addition, a 2-bit length non-signal state space is inserted between frames. In the embodiment, the no-signal state is realized by fixing the output signal of the Manchester code generator 11 to a low level. Insertion of these "0" data and spaces is performed by the Manchester code generator 11 and the counter 6. When the LD signal becomes high level and shifts to the code generation operation, the counter 6 starts counting the clock CLK2 and outputs count data X0 to X5 corresponding to the number of data to the timing control unit 7. Since the clock CLK2 is a clock of twice the data transfer frequency, when the data amount is 24 bits, 48 counts correspond to one frame, and when a space of 2 bits length is included, 50 counts become one unit. The Manchester code generator 11 inputs "0" data only for the first two bit periods based on the count data X0, and then sequentially inputs the SD signals from the shift register 10 to perform Manchester encoding. Further, the timing controller 7 receives the count data X0 to X5 and
During the period of 50 and 50, the CM signal for stopping the code generation operation is set to the low level, and the code output is fixed to the low level.
Insert a bit-length space.

Hereinafter, the receiving apparatus 2 will be described with reference to the drawings. FIG. 5 is a block diagram showing a configuration of the receiving device 2. FIG. 6 is a timing chart showing an operation of extracting a shift clock from a received signal when the waveform distortion is 0%, that is, when the high-level time width of the waveform of the received signal is a predetermined value. In general, it can be considered that the width of the high level and the width of the low level in one data are set to be equal. FIG. 7 shows waveform distortion +
FIG. 8 is a timing chart showing an operation of extracting a shift clock from a reception signal when the time width of the high level of the waveform of the reception signal is 1.5 times the predetermined time width. 9 is a timing chart showing an operation of extracting a shift clock from a received signal when the percentage, that is, the high-level time width of the waveform of the received signal is の of a predetermined time width.

In FIG. 5, the receiving apparatus is externally supplied with a clock CLK8 and operates at the timing. In the embodiment, the clock CLK8 is a clock having a frequency eight times the data transfer frequency. The light receiving element 14 of the receiving device inputs the Manchester optical signal MCD3, converts the signal into a Manchester electric signal MCD4, and inputs the signal to the distortion correction device 4. The distortion correction device 4 extracts the shift clock DC from the Manchester electric signal MCD4 in accordance with the timing of the clock CLK8, and extracts the Manchester electric signal MC.
D6 is output. The WR1TE generation circuit 18 outputs 1 during the period when the shift clock DC is at the high level.
An internal counter which is set to a hexadecimal value “F” and counts down according to the clock CLK8 from the time when the shift clock DC goes to a low level, and when the low level of the shift clock continues for a predetermined time or more, the shift of the shift register 17 is performed. A signal C1 for controlling the operation, a signal C2 for controlling the correction operation of the distortion correction device 4, and a WR signal for permitting the writing of the received data reproduced into an external storage device (not shown) are output.

In the embodiment, as shown in FIGS. 6, 7 and 8, when the count value COUNT of the counter becomes "B", the signal C1 is set to low level to inhibit the shift operation of the shift register 17. At the same time, when the count value COUNT becomes “A”, the signal WR is set to low level to permit writing, and the count value
When T becomes "3", the signal C2 is set to the low level to prepare for the operation of the distortion correction device 4, and writing to the outside where the signal WR is set to the high level is prohibited.

The distortion correction device 4 includes a DC generation circuit 15 and a distortion detection circuit 16. DC generation circuit 15 is light receiving element 14
, A Manchester electric signal MCD5 sampled at the rising edge of the clock CLK8, and a Manchester electric signal MCD sampled at the rising edge of the clock CLK8.
Outputs CD6. The Manchester electric signal MCD
4 and the Manchester electric signal MCD5, and if they are different, it is determined that a transition has occurred in the Manchester electric signal MCD4 and the shift clock DC is raised to a high level. The rising of the MCD4 signal when the signal C2 is at the low level indicates the first "0" of the frame. Also,
When the shift clock DC goes high, the C2 signal goes high. Thereafter, the C2 signal does not go low until the received data enters the space period and the count value COUNT of the internal counter of the WRITE generation circuit 18 becomes "3". The DC generation circuit 15 is set to “6” when the shift clock DC rises and counts down by the clock CLK8 to count data Y0 to Y.
The distortion detection circuit 16 outputs the Manchester electric signal MCD4 and the Manchester electric signal MCD when the count data Y0 to Y2 becomes “3”.
5 are detected and held as an IM1 signal and an IM2 signal, respectively, and applied to the DC generation circuit 15.

If the waveform of the Manchester electric signal MCD4 has no distortion and the high-level time width is a predetermined time width, the IM1 signal goes low as shown in FIG. 6, but the IM2 signal goes high. Level. This case corresponds to a case where the distortion of the received waveform is negligibly small, and the shift clock DC maintains the high level until the value of the count data Y0 to Y2 becomes “1”, and at the time when “1” is detected, the shift clock DC becomes low. Become a level. Thereafter, a value of 6 is set each time the Manchester electric signal MCD4 makes a transition when the clock DC is at a low level, and a down clock is executed, thereby generating a shift clock DC corresponding to the transition of the Manchester electric signal MCD4. When the high-level time width of the waveform of the Manchester electric signal MCD4 is distorted so as to be longer than the predetermined time width, the IM1 signal is at the high level and the IM2 signal is at the high level as shown in FIG. In this case, when the value of the count data Y0 to Y2 becomes "3", the Manchester electric signal MCD4
The shift clock DC is forcibly set to the low level when the low level is detected, and when the high level is detected, the count data Y0 to Y2 is set to “1”.
It keeps high level until it becomes, then it goes to low level. Each time the Manchester electric signal MCD4 makes a transition when the shift clock DC is at the low level, the count data Y0 to Y2 is set to the value "6" and outputs a down-count value. By these operations, the fall of the shift clock DC when the data given by the Manchester electric signal MCD4 transitions from "1" to "0" is advanced, and the shift clock DC corresponding to the transition of the Manchester electric signal MCD4 is obtained. When the high-level time width of the waveform of the Manchester electric signal MCD4 is distorted so as to be shorter than the predetermined time width, as shown in FIG.
The M1 signal goes low and the IM2 signal goes low. In this case, the value of the count data Y0 to Y2 is “3”.
At this time, the level of the Manchester electric signal MCD4 is inspected.
The shift clock DC is maintained at a high level until the value of Y2 becomes "1", and then is set to a low level. Note that each time the Manchester electric signal MCD4 makes a transition when the shift clock DC is at a low level, the count data Y0 to
Y2 is set to the value "6" and outputs a down-count value. By these operations, the Manchester electric signal MCD4
Fall of the shift clock DC when the data given by the clock signal changes from “0” to “1”, the shift clock D corresponding to the transition of the Manchester electric signal MCD4
C.

The shift clock DC generated as described above
Corresponds well to the transition of the Manchester electric signal MCD4, inputs the Manchester electric signal MCD6 to the shift register 17, and sequentially converts the serial data into parallel data by sampling sequentially with the shift clock DC. If there is no transmission data, only the space is transmitted.

As described above, according to the data transfer apparatus of the present embodiment, Manchester in which "0" data is provided in the first two bits of a data frame and a non-signal space is provided in a period corresponding to the last two bits. The first signal "0" after generating and transmitting an electric signal, providing a distortion detection circuit in the receiving device, and detecting a space of the Manchester electric signal.
The distortion pattern is detected depending on whether the high-level time width of the waveform is a predetermined value, longer than the predetermined value, or shorter than the predetermined value. If the high-level time width is longer than the predetermined value, the Manchester electric signal is detected. Makes the fall of the shift clock faster when the data given from “0” changes to “1”, and when the time width of the high level is shorter than a predetermined value, the data given by the Manchester electric signal changes from “1” to “1”. By delaying the fall of the shift clock at the time of transition to "0", even if the waveform of the received Manchester electric signal is distorted, it is possible to extract a shift clock that properly corresponds to the transition. Therefore, the influence of the light amount in the transmission device and the characteristics of the light receiving element in the reception device can be eliminated, and a data transfer device that does not require adjustment work or consideration for the installation environment can be realized.

Although the description has been made in the embodiment that the non-signal space is fixed to the low level, it goes without saying that the space may be fixed to the continuous high level corresponding to the no signal.

[0021]

As is apparent from the above description, the present invention relates to a data transfer apparatus which converts Manchester-coded serial data into an optical signal and transmits / receives the signal via an optical fiber. The continuous "0" data is transmitted before the transmission data body, and the output signal is fixed to no signal for a period corresponding to at least 2 bits after the transmission data body, and the output signal is output when there is no transmission data. And the receiving device measures the high-level time width of the first detected “0” data after two or more bits of no-signal at the receiving device and outputs the predetermined high-level time width. If the time is longer than the time width, when the data of the subsequent received signal changes from “1” to “0”, the fall of the reference clock extracted from the received signal is advanced, Also, when the high-level time width of the first detected “0” data after the no-signal of 2 bits or more is shorter than the predetermined time width, the data of the subsequent received signal changes from “0” to “1”. When the data transfer device is equipped with a waveform distortion correction device that accelerates the fall of the reference clock extracted from the received signal when the received signal changes, even if the waveform of the received Manchester electrical signal is distorted, A data transfer device that can correctly extract the corresponding clock, removes the influence of the light amount in the transmission device and the characteristics of the light receiving element in the reception device, and eliminates the need for adjustment work and installation environment that take those characteristics into account. realizable.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a data transfer device of the present invention.

FIG. 2 is a block diagram showing a configuration of a transmission device in one embodiment of the data transfer device of the present invention.

FIG. 3 is a timing chart showing an operation of generating a Manchester electric signal of the transmission device in one embodiment of the data transfer device of the present invention.

FIG. 4 is a schematic diagram showing a data configuration in an embodiment of the data transfer device of the present invention.

FIG. 5 is a block diagram showing a configuration of a receiving device in one embodiment of the data transfer device of the present invention.

FIG. 6 is a timing chart showing the operation of the receiving apparatus in one embodiment of the data transfer apparatus according to the present invention when the waveform distortion is 0%.

FIG. 7 is a timing chart showing the operation of the receiving device in one embodiment of the data transfer device of the present invention in the case of waveform distortion + 50%.

FIG. 8 is a timing chart showing the operation of the receiving apparatus in one embodiment of the data transfer apparatus according to the present invention for the case where the waveform distortion is -50%.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmitting device 2 Receiving device 3 Optical fiber 4 Distortion correction device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H03M 5/12 H04B 10/00

Claims (1)

(57) [Claims] 1. A data transfer device which converts Manchester-coded serial data into an optical signal and transmits / receives the signal via an optical fiber. If there is transmission data, continuous "0" data of 2 bits or more is provided before the transmission data body. A transmission device for transmitting and fixing the output signal to a no signal during a period corresponding to at least a 2-bit length after the transmission data body, and for fixing the output signal to a no signal when there is no transmission data, The receiving device measures the high-level time width of the first detected “0” data after a no-signal of 2 bits or more, and if the high-level time width is longer than a predetermined time width, the subsequent reception signal is measured. Data is "1"
From “0” to “0”, the fall of the reference clock extracted from the received signal is advanced, and the high-level time width of the first detected “0” data after the no-signal of 2 bits or more is equal to the predetermined level. If it is shorter than the time width, when the data of the subsequent received signal changes from “0” to “1”,
A data transfer device comprising: a waveform distortion correction device that hastens the fall of a reference clock extracted from a received signal.