JPH0231828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission line disconnection detection method, and an object thereof is to provide a method that can quickly detect a transmission line disconnection when data is repeatedly transmitted via the transmission line.

A conventional data transmission/reception method is shown in FIG. In this figure, the transmitting side (TX) and the receiving side (RX) are connected by a total of five signal lines, four transmission lines _l1 to _l4 and one strobe signal line _l5 . On the transmitting side (TX), each 4-bit digit series data D ₁ ,
D ₂ , D ₃ . . . are applied in bit parallel to the transmission lines l ₁ to _{l 4} as shown in FIG.
At the same time, the strobe signal _P1 of FIG. 2b is applied to the strobe signal line _l5 . Receiving side (RX)
The configuration is such that each time the strobe signal P is generated on the strobe signal line _l5 , the states of the four transmission lines _l1 to _l4 at that time are read as data. However, conventionally, during such data transmission, the transmission line
No disconnection checks were performed for l ₁ to _{l 4} .
If the disconnection occurs, there is a risk that erroneous data will be read on the receiving side (RX), and the current situation is that it is not possible to interrupt processing based on this erroneous data.

Therefore, the present invention has developed a system that uses N transmission lines for sequentially transmitting N-bit data in which all bits do not invert to logic level "H" at the same time. During the start time, all N transmission lines are inverted to logic level "H" for at least a predetermined time on the transmitting side, and the N transmission lines are not simultaneously inverted to logic level "H" for a predetermined time or more on the receiving side. A specific embodiment of the present invention will be described below with reference to FIGS. 3 and 4. Note that an example in which data is transmitted from an electronic toll scale to a printer device will be described here.

1 is an electronic toll scale as a transmitting side, 2 is a printer device as a receiving side, and l ₁ to _{l 4} are four transmission lines connecting the electronic toll scale 1 and the printer device 2. The electronic toll scale 1 side has data such as tare, weight, price, unit price, etc. as data to be transmitted, and the microcomputer A on the electronic toll scale 1 side has a data sending routine configured as follows. There is.

In microcomputer A, the order of data to be transmitted is tare → weight → price → as shown in Figure 4 a.
It is determined that the cycle is repeated in the order of the unit price, and the time t ₂ between the end time of one data transmission and the start of the next data transmission is F ₁₆ [If written in bits, the transmission line l ₁ to l ₄ The configuration is such that all signals are held at a logic level of "H" for transmission.
Here, the data is transmitted in parallel bits and serially, and each data transmission time _t1 is equal, and the time _t2 until the next data is also equal.
Further, the microcomputer A generates a strobe signal _P1 on the strobe signal line _l5 as shown in FIG. 4b in synchronization with the transmission of each data, as in the conventional case.

On the printer device 2 side, which reads the above data via transmission lines _l1 to _l4 , a microcomputer B
The states of the transmission lines _l1 to _l4 at the timing when the strobe signal P is generated on the strobe signal line _l5 are read each time as data. In addition, on the printer device 2 side, an AND gate 3 performs the AND of the transmissions l ₁ to l ₄ , and when this AND gate 3 detects a match as shown in FIG. Trigger the multivibrator 4 as shown in FIG. 4d. Here, the specified time T of the monostable multivibrator 4 is set to T > t ₁ + t ₂ , so if the transmission lines l ₁ to l ₄ are normal, it will be retriggered within the specified time T and the monostable multivibrator 4 will be activated again. Although the output Q of the stable multivibrator 4 is maintained at “H” level,
If at least one of the transmission lines l ₁ to _{l 4} is disconnected, the monostable multivibrator 4 will not operate for the specified time T.
Since it is not retriggered within this time, the output Q returns to logic level "L". At the negative edge when the output Q of the monostable multivibrator 4 returns to logic level "L", the pulse generator 5 generates an interrupt pulse.
The occurrence of P ₂ is indicated. This interrupt pulse _P2 acts on microcomputer B as an interrupt signal, and the microcomputer B to which the interrupt was applied
is configured to abort the normal reading operation using the strobe signal _P1 and execute a routine for notifying disconnection. The disconnection notification routine may include, for example, an operation of printing out a code indicating a transmission disconnection.

In the above example, over the entire area during time t ₂
Although the configuration is configured to transmit F ₁₆ , it is only necessary to transmit F 16 during time t ₂ , which is longer than the time required for the AND gate 3 to read the data accurately.

As described above, according to the present invention, when at least one transmission line is disconnected, this disconnection state can be quickly detected, and an instruction can be given to interrupt processing operations due to erroneously read data.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of the transmitting side and receiving side of a conventional data transmission/reception system, Fig. 2 is a waveform diagram of Fig. 1, Fig. 3 is a block diagram of a specific embodiment of the present invention, and Fig. 4 a
.about.d are diagrams of the transmission format of FIG. 3 and main part waveforms inside the receiving side. 1...Electronic toll scale [sending side], 2...printer device [receiving side], 3...and gate, 4...
...monostable multivibrator, 5...pulse generator, A, B...microcomputer, _l1 to _l4 ...
...Transmission line, l ₅ ... Strobe signal line, P ₂ ... Interrupt pulse.

Claims (1)

[Claims] 1 N transmission lines that sequentially transmit N-bit data in which all bits do not invert to logic level "H" at the same time are connected between the data transmission end time and the next data transmission start time each time transmission of one data is completed. The transmission side inverts all of them to logic level "H" for at least a predetermined period of time, and the reception side detects that the N transmission lines do not simultaneously invert to logic level "H" for a predetermined period of time or more. A transmission line disconnection detection method that determines that a disconnection has occurred.