JPS62235846A - Controlling system for data strobe timing of communication control equipment - Google Patents

Abstract

PURPOSE:To automatically adjust out-of phase between data and a strobe timing signal even if a signal speed or a cable length to an opponent device changes by setting a timing signal selected among the plural timing signals whose phases differ to a data strobe timing signal and exchanging data. CONSTITUTION:A timing selection control means 7 which outputs a selection signal to select the data strobe timing signal, and a timing selection means 8 which sets plural timing signals with different phases to input and select the target timing signal with the aid of the signal selected among them are provided. Data exchange is controlled by setting the timing signal selected by the timing selection means 8 to the data strobe timing signal. Thus, only by connceting the length of a cable which a user wants to use between a ccmmunication control equip ment. and the opponent equip ment, a suitable data strobe timing can be selected, which corresponds to the cable length and a circuit speed.

Description

[Detailed Description of the Invention] [Industrial Application Field]: The present invention relates to a data strobe timing control method for a communication control device, and a data strobe timing control method for a communication control device that is particularly suitable when using a high line speed. Regarding.

[Conventional technology]

In a general data communication system, a communication control device is connected to a central processing unit and a line termination device (DCE).
), the DCE is connected to a partner DCE through a digital data exchange network, and a partner device such as a terminal device is connected to the DCH.

In step 2, DCE is a communication control device or terminal device (DC
When viewed from E, it converts a digital signal from a communication control device (also a type of terminal device) into a digital signal suitable for transmission, or vice versa.

In recent years, CC1TT-Recommendation x, 21 interface level 1 has also been widely used as a line eraser face (interface between communication control device and PCE) of communication control devices in such data communication systems. In addition, compared to other line interfaces, this x,21 interface level 1 allows data communication at higher speeds and over longer distances. Furthermore, in test systems and the like, there is an increasing number of cases in which the communication control device of each system and the other device are directly connected with a cable without using a modem or the like.

In this way, one communication control device and the other device (or DCE)
When connecting x, 21 interface level 1 with a cable, in the communication control device.

Conventionally, the circuit configuration has been such that data is transmitted at the rising edge of an element timing signal from a partner device corresponding to DCE or DCH, and data is received at the falling edge.

[Problem that the invention seeks to solve]

In the prior art described above, when an It was necessary to shorten the distance. This will be explained with reference to FIGS. 7 and 8.

FIG. 7 shows a conventional communication control device 1 and DCE or DCE
Partner device I with a corresponding signal (hereinafter referred to as DCE)
2 is a diagram showing where 2 are connected.

T, C, R, i, S are interface signals, T
, C is the communication control device g! 1 is data and control signals sent to DCE2, and R2i is data and display signals received from DCE2. S is an element timing signal and is normally sent from the DCE2.

This is because, as described above, the element timing signal S and the transmission data T of the communication control device 1 are in opposite directions.

In terms of DCE2 mainly due to cable delays etc.

This causes the transmission data T and the element timing signal S to be out of phase, and in the case of high line speeds, restrictions on the distance between devices become stricter. This situation is shown in FIG.

Figure 8 (a) is the case when the cable length is short, and Figure 8 (b) is
is the case when the cable length is long. In Figure 8, (a
) The element timing signal S of DCE2 shown in (c
), the data T shown in (d) arrives at the communication control device 1 with a delay and is sent out using the element timing signal S.
It returns to DCE2 with a delay as shown in (b). Normally, data is transmitted at the rising edge of the element timing signal S and received at the falling edge, so the cable length is short or the line speed is low, as shown in Figure 8 (a), and there is a delay compared to the 1-bit length T. In other words, if the degree of phase shift T2 is negligible, reception can be performed correctly, but as shown in FIG.
2 is close to half of Ti, the element timing signal S at the X, 21 interface has a duty ratio of 50.
%, it will not be possible to receive the data correctly.

In order to avoid the above problem, it is necessary to adjust the phase of the element timing signal S and the transmission data T in DCE2, but since the relative magnitude of T2 to Tyu changes depending on the cable length and line speed, Adjustment was troublesome.

This problem arises when the communication control device is connected to the communication line via DCE.
There is no need to lengthen the distance between the communication control device and 00 because it is between the CEs, so it can be solved by shortening the distance between the communication control device and the DCE, and it does not pose a particular problem. However, when directly connecting the communication control device of each system and the other device as described above, adjustments must be made every time the signal speed or cable length changes.
Alternatively, there is a problem in that the distance between devices must be kept short.

An object of the present invention is to enable a communication control device to automatically adjust the phase shift between data and strobe timing signals even if the signal speed or cable length between the communication control device and the other device changes.
Therefore, it is an object of the present invention to provide a data slope timing control method that does not require shortening the distance between devices.

[Means for solving problems]

The above object provides a cable length table F means for outputting a cable length display signal indicating the cable length to a communication control device; a communication speed display means for outputting a data communication speed signal indicating the communication speed of the data signal; Input the display signal and data communication speed signal.

A timing selection control means for outputting a selection signal for selecting a data strobe timing signal, and a timing selection means for inputting a plurality of timing signals having different phases and selecting a desired timing signal from among them using the selection signal. This is achieved by

[For production]

The communication control device controls data transmission and reception using the timing signal selected by the timing selection means as a data strobe timing signal. This makes it possible to select the appropriate data strobe timing according to the cable length and line speed by simply connecting the cable of the desired cable length between the communication control device and the other device. is not necessary, and there is no need to shorten the distance between devices.

〔Example〕

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

FIG. 1 shows a configuration diagram of an embodiment of the present invention. In FIG. 1, a communication control device 1 and a partner device (hereinafter referred to as DCE) 2 having a DCE or DCE-equivalent signal are x, 21 interfaces. 1 communication control device 1 connected by a face cable 11 has a data receiving section 3. Data transmitter 4. Data communication speed display circuit 5, timing selection control circuit 7, timing selection circuit 8, reception circuit 9. It is equipped with an inverter 10, and furthermore, a cable length display circuit 6 is connected to the connector portion.

The data communication speed display circuit 5 is a circuit that outputs a speed signal of the data communication speed, and is, for example, a register or switch in which a program value is set. In 2N, a 4-bit register is used, and a pattern assigned to each data communication speed as shown in FIG. 4 by a program is output as a speed signal.

The cable length display circuit 6 is placed on the communication control device side of the X, 21 interface cable 11, and is a circuit that outputs a cable length display signal that indicates the cable length. A pattern corresponding to the cable length is connected to the input Ov or other potential by wiring, and a cable display signal is output. Here, we will use the 4-bit pattern assigned to each cable length as shown in Figure 5.
111" is +5V at the connector part of cable 11
It is assumed that "0" indicates that a cable length display signal is output by wiring to Ov.

The timing selection control circuit 7 is a circuit that outputs conditions for selecting the data strobe timing signal 8.4 to be applied to the data transmission Is4 from the communication speed signal of the data communication speed display means 5 and the cable length display signal of the cable length display circuit 6. It is. At the knee, a ROM (read-only memory) outputs a 1-bit data strobe timing selection signal S3 with the data communication speed signal as the upper address (4 bits) and the cable length display signal as the lower address (4 bits). Suppose we use This ROM has a margin of 25% for data T from the communication control device 1 with respect to the element data and timing signal S in the DCE 2, which is determined by the cable length and line speed (i.e., as shown in Figures 1 and 3). Fall of element timing signal S in DCE2, conversion of data T, time to α TltT
4, where the smaller value (T3 in Figure 3) is 25% of 1 bit time T1), and the margin is 2.
Calculate in advance and write "1" or "O" so that if it is less than 5%, "1-" will be output, and if it exceeds 2.9%, "0" will be output. T2 in the figure is.

The theory in Figure 8! As mentioned above, this is the delay time of the signal in the cable. Note that in the case of the knee, an example is shown in which the delay time T2 on the cable is smaller than 1 bit time Ti, but if it is larger than T1.

T2 is the value obtained by subtracting an integral multiple of T1 from the delay time T2.
If so, they can be treated the same.

, the margin due to the combination of the above cable length and line speed, and the timing selection signal (ROM) determined by this.
The output of 7 is shown in FIG. 6. In this example, calculations are made using a cable with a delay time of 5 nanoseconds/m. ・The timing selection circuit 8 outputs a timing selection signal. This is a selector that selects the element timing signal S when S3 is "0" and selects the element timing signal S2 when it is ``1'', and outputs the transmission data strobe timing S. Sl is the element that the DCE 2 sends. The timing signal S is received by the receiving circuit 9, and S2 is a signal obtained by inverting the phase of the signal S by the inverter 10.

The operation shown in FIG. 1 will be described below with reference to FIG. 2 when the margin between the element timing signal S and data T in DCE2 is 25% or less and when it exceeds 25%.

FIG. 2(a) is a time chart when data communication is performed in the configuration shown in FIG. 1 at a data communication speed of 1 megabit for 1 second and a cable length of 50 m.

A speed signal with a pattern of "0100" is output.

Further, the cable length display circuit 6 outputs a cable length display signal in a pattern of '0011'.

When this speed signal and cable length display signal are input to the address of the ROM of the timing selection circuit 7, the timing selection signal S3 which is the output of this ROM is shown in FIG.
becomes “1”, and the timing selection circuit 8 selects the transmitter 4.
The element timing signal S2 is the transmission data strobe timing S.

The transmission data D1 is transmitted.

Due to the delay time T3 on the cable, this transmission data processing becomes D2 at the point of DCE2. In this example, T□=100
0 nanoseconds (1000 kilobits/second).

T, ==500 nanoseconds (50m cable), T2 is T
50% of the total cost. Since the element timing S in the X, 21 interface has a duty ratio of 50%,
As is clear from the figure, in the DCE2, the margin D2 between the element timing signal S in the DCE2 and the transmission data D2 from the communication control device 1 is 50%, which means that data can be correctly received.

Transmission data D, , D4 are data when transmitted at the rising edge of S as in the past, and transmission data D from communication control device 1 is transmitted at DCE2 due to delay time T2 on the cable with respect to element timing signal S in DCE2. In this respect, it is D4. At this time, the element timing signal S
The margin of the transmission data D4 is 0%, which prevents data errors from occurring.

FIG. 2(b) shows a case where the data communication speed is 1 mebit/sec and the cable length is 20 m in the configuration of FIG. 1. Similarly to the above, in FIG. 1, the data communication speed display circuit 5
, the speed signal “010” output from the cable display circuit 6
0'' and the cable length display signal ``0010'' are input to the address of the ROM of the timing selection circuit 7, the element timing selection signal S becomes 0'', and the data transmitter 4 outputs S as the transmission data strobe timing signal s4.
□ is given, and transmission data D1 is transmitted. This is the same as transmitting at the rising edge of the element timing signal S1 as before, but in this example, Tuni is 1000 nanoseconds, T, = 200 nanoseconds, and T2 is 20% of T, so from the figure As is clear, in DCE2, the cable delay time T2 between the element timing signal S and the transmission data D1
The margin with respect to the subsequent transmission data 9D2 is 30%, and no data error will occur.

In this way, by controlling the transmission data strobe timing of the communication control device using the method of the present invention, the data margin can be set to 25% or more regardless of the data communication speed and cable length, resulting in good data communication. It can be performed.

〔Effect of the invention〕

According to the present invention, by simply connecting a cable of the desired cable length to the communication control device, it is possible to select an appropriate element timing signal for data transmission and reception according to the cable length and line speed, thereby reducing the distance between devices. There is no need to shorten the length, and troublesome adjustments can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram when a communication control device and a line termination device according to an embodiment of the present invention are connected, Fig. 2 is a time chart explaining data transmission according to Fig. 1, and Fig. 3 shows a data margin. A time chart to be explained, FIG. 4 is a diagram showing an example of a pattern set in the data communication speed display circuit of FIG. 1, and FIG. 5 is a diagram showing an example of a pattern set in the cable length display circuit of FIG. 1. Figure 6 is a diagram showing the data written to the ROM constituting the timing selection control circuit in Figure 1 and the margin of the data output at that time. Figure 7 is a diagram showing the conventional communication control device and line. FIG. 8 is a configuration diagram when a terminal device is connected, and is a time chart showing the deviation between the element timing signal and data due to the cable delay in FIG. 7. 1...Communication control device, 2...Line termination device, 3.
...Data receiving section, 4...Data transmitting section. 5... Data communication speed display circuit, 6... Cable length display circuit, 7... Timing selection control circuit, 8...
...timing selection circuit, 9...reception circuit, 10.
...Inverter, 11...Cable. Figure 2 Figure 4 Figure 5 Figure G

Claims (1)

[Claims] (1) In a communication control device connected to a partner device by a cable, a cable length display means for outputting a cable length display signal, a data communication speed display means for outputting a data communication speed signal, and the cable length display signal and data timing selection control means for outputting a data strobe timing selection signal based on a communication speed signal; and timing selection means for selecting a timing signal indicated by the timing selection control signal from among a plurality of timing signals having different phases. A data strobe timing control method for a communication control device, characterized in that data transmission and reception is performed using the selected timing signal as a data strobe timing signal.