JP2605051B2 - Communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ISDN (Integrated Services Digital Network).
k) It relates to a compatible communication device.

[Prior Art] Conventionally, in a frame synchronization circuit of this type of communication apparatus, as shown in FIG. 5, a frame 50 is supplied to a load terminal 53 of a counter 50 for counting a synchronization clock synchronized with a bit of a frame of a received signal. Inside, a violation detection signal 51 indicating that a violation has occurred was input.

[Problems to be Solved by the Invention] Therefore, due to noise or the like on the transmission path, "0" (zero) or "1" of each bit constituting the frame changes on the transmission path, and the bioration detection signal When 51 goes high at an irregular position, it is in sync
The disadvantage is that the synchronization establishment signal 52 is not always output.

The present invention has been made in view of the above conventional example, and provides a communication device capable of reliably establishing frame synchronization in a short time from a state in which frame synchronization has not been established, without malfunction due to noise or the like on a transmission path. The purpose is to do.

[Means for Solving the Problems] In an ISDN-compatible communication device that performs communication using a frame of a predetermined bit length, a counter that counts a synchronization clock of a received signal and outputs a carry signal when the set predetermined value is counted. A frame synchronization that outputs an out-of-sync signal indicating that frame synchronization has not been established or a synchronization establishment signal indicating that frame synchronization has been established, based on the carry signal and the frame bit detection signal of the counter. Detecting means for setting a predetermined value corresponding to one frame bit length to the counter in response to the frame bit detection signal when the out-of-sync signal is output from the frame synchronization detecting means; When the synchronization detection signal is output from the synchronization detecting means, the carry signal of the counter is output. Means for setting the predetermined value in the counter in accordance with the following.In a state where frame synchronization is not established, the frame synchronization detecting means outputs the out-of-synchronization signal, and outputs the frame bit detection signal and the frame bit detection signal. When a carry signal is detected, the synchronization establishment signal indicating that frame synchronization has been established is output.

[Operation] In the above configuration, the frame synchronization detecting means outputs an out-of-synchronization signal in a state where the frame synchronization is not established, whereby the counter corresponds to one frame bit length in accordance with the frame bit detection signal. A predetermined value is set, and when a frame bit detection signal and a carry signal are detected next, a synchronization establishment signal indicating that frame synchronization has been established is output.

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

[Explanation of Communication Device (FIG. 2)] FIG. 2 is a block diagram showing a schematic configuration of the communication device of the embodiment.

In the figure, reference numeral 10 denotes transmission / reception to / from another terminal via a communication line 17 in the entire communication apparatus of the embodiment. A line control unit 11 includes a network control unit (NCU), a modem, and the like, and controls transmission and reception of data with the communication line 17. Reference numeral 12 denotes a bioration detection unit, which outputs a bioration detection signal 20 to the synchronization signal creation unit 13 when detecting a violation signal. Reference numeral 13 inputs a bioration detection signal 20 from the bioration detection unit 12 and a synchronization clock 21 synchronized with the frame bit from the line control unit 11, and detects that synchronization has been established. Control signal 14 for establishment signal 22
Output to

The control unit 14 controls the entire communication device 10 and inputs and outputs transmission / reception data 23 to and from the line control unit 11. 16
Reference numeral denotes an input / output unit provided with a CRT, a keyboard, and the like, in which an operator inputs a function instruction, inputs transmission data, and displays and outputs received data. Reference numeral 15 denotes a storage unit that stores transmission data input from the input / output unit 16 and reception data input from the line control unit 11.

[Description of Synchronization Signal Creation Unit (FIGS. 1 to 4)] FIG. 1 is a diagram showing a configuration of a synchronization signal creation unit 13 of the communication apparatus 10 according to the embodiment, and the same parts as those in FIG. Is shown.

In the user network interface in the ISDN basic access, the signal forms an AMI (Auternate Mark Inversion), which is a form in which the polarity is inverted for each mark signal as shown at 30 in FIG. . AMI biorational is a violation of AMI rules and is shown in Fig. 3 (A).
This is the case where the same polarity is repeated twice as indicated by 32 in FIG.

This AMI bioration is output from the transmitting side as a frame synchronization signal. The receiving side detects this AMI bioration and detects frame synchronization. In this embodiment, one frame has 48 bits, and two biorations exist in one frame. This is shown in the timing chart of FIG. 3B, which shows a frame bit 33 which is the head of the frame, and a bioration bit 35 generated after the frame balance bit 34 following the frame bit 33. . As described above, one frame includes the frame bit 33 and the bioration bit of the bit 35. This bioration bit 35 is guaranteed to be within 14 bits of the bit and frame bits.

In the circuit shown in FIG.
Is input, when the out-of-synchronization signal 8 is turned on, that is, when synchronization is not established, the AND circuit 2 opens and the load signal 6 is output to the counter 4 through the OR circuit 3. As a result, the number of bits for one frame ("48" in the embodiment) is set.

On the other hand, the AND circuit 1 is opened when the synchronization is established (when the synchronization establishment signal 22 is at a high level) and the ripple carry signal 7 of the counter 4 is turned on, whereby the number of bits of one frame (“48 ") Is loaded.
The comparison circuit 5 outputs the synchronization establishment signal 22 when the carry signal 7 from the counter 4 is turned on when the bioration detection signal 20 is input, and the carry signal 7 and the bioration detection signal 20 are simultaneously output. If not, the out-of-sync signal 8 is turned on.

This operation will be described with reference to the timing chart of FIG.

In the figure, 40 is a frame bit indicating the start of one frame,
Reference numeral 41 denotes a bioration bit which is guaranteed to occur within 14 to 14 bits of the frame bit. The bioration detecting section 12 does not detect a bioration bit 41 within 14 bits from the frame bit 40 as a bioration.

At timing T1, the bioration detection signal 20 based on the frame bit 40 is output. At this time, if synchronization is not established, the carry signal 7 of the counter 4 is not output. However, even in this case, the load signal 6 is output through the AND circuit 2, and the bit number "48" for one frame is set in the counter 4. Therefore, at the start of the next frame (timing T2), the ripple carry signal 7 of the counter 4 and the bioration detection signal 20 are output at the same time, so that the synchronization establishment signal 22 is output from the comparison circuit 5. .

As described above, according to the present embodiment, the load signal of the counter that counts the clock synchronized with the frame bit of the synchronization signal generator, the bioration detection signal when the synchronization is lost, and the ripple carry output of the counter itself when synchronization is established. To load the bit length of the frame into the counter and compare the ripple carry signal of the counter with the bioration detection signal to detect synchronization, thereby increasing the reliability of frame synchronization and reducing the time required for synchronization detection. There is an effect that it can be shortened.

[Effects of the Invention] As described above, according to the present invention, it is possible to reliably establish frame synchronization in a short time from a state where frame synchronization has not been established, without malfunction due to noise or the like on a transmission path. There is.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a synchronization signal generating unit of the communication device of the embodiment, FIG. 2 is a block diagram showing a schematic configuration of the communication device of the embodiment, and FIGS. FIG. 4 is a diagram for explaining a ration signal, and FIG.
FIG. 5 is a diagram showing an example, and FIG. 5 is a diagram showing a configuration of a synchronizing signal generator of a conventional example. In the figure, 1, 2,... AND circuit, 3... OR circuit, 4... Counter, 5... Comparison circuit, 6... Load signal, 7. Apparatus, 11 ... Line control unit, 13 ... Synchronization signal creation unit, 14 ...
Control unit, 15 storage unit, 16 input / output unit, 17 communication line, 20 bioration detection signal, 21 synchronization clock, 22 synchronization probability signal, 23 transmission / reception data, 33,4
0: Frame bit, 32, 35, 41: Bio-rate bit.

Claims (1)

(57) [Claims] Communication is performed using a frame having a predetermined bit length.
In a communication device compatible with ISDN, a counter that counts a synchronous clock of a received signal and outputs a carry signal when a set predetermined value is counted, and a frame based on the carry signal and a frame bit detection signal of the counter. Frame synchronization detecting means for outputting an out-of-synchronization signal indicating that synchronization has not been established or a synchronization establishment signal indicating that frame synchronization has been established; and the out-of-synchronization signal has been output from the frame synchronization detecting means. Means for setting a predetermined value corresponding to one frame bit length in the counter according to the detection signal of the frame bit, and when the synchronization establishment signal is output from the frame synchronization detection means, the counter carries the signal. Means for setting the predetermined value in the counter according to a signal, In a state where the period has not been established, the frame synchronization detecting means outputs the out-of-synchronization signal, and when detecting the frame bit detection signal and the carry signal, indicates that the frame synchronization has been established. A communication device for outputting an establishment signal.