JPS5954354A - Signal transmitting method - Google Patents

Abstract

PURPOSE:To prevent malfunction due to noise, by confirming that a power supply of an opposite device is at a normal voltage level, then receivig a signal from the opposite side. CONSTITUTION:The level of a power supply voltage of a power supply 15A is discriminated at a power supply voltage level discriminating circuit 16A, and attains to a digital power supply voltage level display signal SPA. The display signal SPA is transmitted to the opposite device 11B. The device 11B receives the display signal SPA at a discriminating circuit 17B and generates a gate signal SGB to switch a gate 18B. Further, a signal from the device 11A is received in response to the gate signal SGB.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a signal transmission method, particularly to a signal transmission method during power-on/power-off.

(2) Background of the Technology In a signal transmission system in which two devices (referred to as A and B) are connected via a transmission path, device A and device B may be driven by separate power supplies. For example, if these devices A and B are placed apart from each other.

In such a case, it is almost impossible for devices A and B to be powered on or powered off at exactly the same timing, and one of them is powered on or powered off first or later. In this case, since noise is generally included in the power supply voltage when the power is turned on or turned off, noise from device A or B may be transmitted to the other device (which is already in a normal operating state, that is, whose power supply voltage has been determined). received by B or A),
It may cause malfunction.

Therefore, some kind of noise countermeasure is required when powering on and off the device. The present invention refers to a signal transmission method that takes such noise countermeasures.

(3) Prior Art and Problems Conventionally, as a countermeasure against the above-mentioned noise between device A and device B, a method has been adopted in which redundancy is provided in the combination of signals in the protocol between these devices. In other words, the transmitting side transmits a predetermined signal pattern at the start of an operation sequence, and when a signal that does not match this signal pattern is received, it is determined to be noise, and such a signal is not accepted by the receiving side. The idea is to make sure that there is no such thing. However, such noise countermeasures have two problems. The first problem is that if the above signal pattern is always transmitted at the beginning of an operation sequence, it imposes restrictions on the operation sequence, which ultimately reduces its versatility and reduces the degree of freedom that it can be applied to any device. This means that you will lose the The second problem is that when device A and device B are inserted into a transmission path wired between a central processing unit (CPU) and an input/output device (I/O), Or, measures must be taken in advance to prevent the CPU or I/O from malfunctioning when the signal pattern transmitted from B is received by the CPU or I/O. . Note that the case of inserting devices A and B (or more devices) into the transmission path as described above is often done when the distance between the CPU and I/O is large. It is often inserted to play the role of relay amplification and interface in signal transmission.

(4) Purpose of the Invention The object of the present invention is to propose a signal transmission method that can simultaneously solve the first and second problems mentioned above.

(5) Structure of the Invention In order to achieve the above object, the present invention provides a signal transmission method in a device A and a device B that mutually exchange signals, in which the device A (or B) is connected to the power source of the device B (or A). is at the correct voltage level, then connect device B (or A
) is characterized in that it accepts signals from.

(6) Embodiment of the Invention FIG. 1 is a block diagram showing an example of a system to which the method of the invention is applied. In the figure, 11A and 11B are a device (A) and a device (B) that mutually exchange signals, and a transmission line 12 connects them. Device 1
1A and 11B are, for example, a central processing unit (CPU) 1
3 and an input/output device (I/O) 14. As mentioned above, this is done by the CPU 13.
This is to extend the transmission distance between the I/O 14 and the I/O 14. However, the gist of the present invention can of course be applied to the case where only the device 11A, the device 11B, and the transmission path 12 are present. In this case, device 11A is the CPU, device 11B is the I/
You can consider each as O. Or devices 11A, 11
Both B may be considered to be CPUs or I/Os.

By the way, if the devices 11A and 11B are driven by separate power supplies (P) 15A and 15B, the above-mentioned problem occurs due to noise when the devices are turned on or turned off. This noise is shown in FIG. 2a).

FIG. 2 is a waveform diagram used to explain the method of the present invention. Figure 2 a) shows an example of the waveform of the power supply voltage.
In most cases, noise N is accompanied. There are various possible causes of noise N, but for example, it is thought that it is caused by rising to a specified power supply voltage through various thresholds in the power supply circuit. In any case, it is clear that if such noise N is transmitted to the other party's device, it will induce malfunction.

Therefore, the present invention monitors the power state of the other party's device and does not accept signals from the other party's device when the other party's device is not in a normal power state.

In other words, the device 11A (or 11
Various signals such as command data, status information, or data from I/O 14 (or C
The data will not be transmitted to the PU 13), and malfunctions will be prevented. According to the embodiment, the power supply voltage of the power supply 15A (15B) is level determined by the power supply voltage level determination circuit 16A (16B), and becomes a digital power supply voltage level display signal SPA (SPB). If the power supply voltage level is above the normal voltage level (L) in Figure 2 a), logic “1”;
If it is less than that, it is logic "0", therefore, Fig. 2b)
A display signal SPA (SPB) as shown below is obtained. The display signal SPA (SPB) is transmitted to the other party's device 11B (11A).

In the other party device 11B (11A), the display signal SPA (S
PB) is received in the determination circuit 17B (17A), and a gate signal SG for opening/closing the gate 18B (18A)
Generate B(SGA). FIG. 3 is a block diagram showing an example of the determination circuit (17A, 17B) in FIG. 1. Since the determination circuits 17A and 17B have exactly the same configuration, the determination circuit 17B will be exemplified. Judgment circuit 17
B is a counter 31 and a ROM (read only).
memory) consists of 32. Counter 31 is logic “1”
As long as the display signal SPA of "" continues to be received, the count value is counted up, but if even one bit of the display signal SPA of logic "0" is received, the count value is instantly cleared to zero. The numerical value (output) is input to the ROM 32, and the ROM 32 outputs a logic "1" gate signal SGB when the counted value becomes larger than a predetermined value C. On the other hand, when the counted value becomes zero, the logic "0'' gate signal SGB is output.

By employing such a determination circuit 17B (17A), a gate signal SGB (SGA) as shown in FIG. 2c) can be obtained. In c) of the same figure, TC indicates the period until the aforementioned predetermined value C is reached.

After the period TC, the power supply voltage rises sufficiently and the normal operating state of the device can be ensured.

On the other hand, when the power is turned off (Poff), the gate signal SGB
(SGA) immediately becomes logic "0" when the signal SPA becomes logic "0" for the first time. Such a gate signal SGB(S
By using GA) for the gate 18B (18A),
For example, a signal from the device 11B whose power supply voltage has not risen sufficiently will not be accepted by the gate 18A of the device 11A, and a signal from the device 11B that includes the noise N when the power is turned on will not only be transmitted to the CPU 13 within the device 11A. I can't even get it across. This is the same when the power supply voltage of the device 11A is not sufficiently raised, and the signal from the device 11A containing noise is not transmitted to the I/O 14 as well as inside the device 11B.

On the other hand, for example, when the power of the device 11B is turned off (Poff), the gate 18A in the device 11A is immediately closed, and the signal from the device 11B containing the noise N generated when the power is turned off is transmitted not only to the inside of the device 11A but also to the CPU 13. I can't even get it across.

This also applies to the case where the device 11A is powered off, and the signal from the device 11A containing noise is transmitted to the device 11B.
Of course, it is not transmitted to the I/O14 either. In addition, 19A,
19B is a driver circuit for a signal to be transmitted.

Although FIG. 1 shows an example in which the transmission line 12 is formed of a multi-core cable, other examples are also possible and are not affected by the form of the transmission line.

FIG. 4 is a block diagram showing an example of a system in which the transmission path of FIG. 1 is simplified. This simplification is achieved based on the so-called time division multiplexing method, which allows parallel/
Serial conversion circuits (P/S) 41A, 41B and serial/parallel conversion circuits (S/P) 42A, 42B are introduced. However, the method of the present invention can be applied as is.

(7) Effects of the Invention As described above, according to the present invention, a signal transmission method capable of solving the first and second problems described above is realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a system to which the method of the present invention is applied, FIG. 2 is a waveform diagram used to explain the method of the present invention, and FIG. 3 is a determination circuit (17A,
FIG. 4 is a block diagram showing an example of a system in which the transmission path of FIG. 1 is simplified. 11A, 11B...device, 12...transmission line, 15A, 15B
...Power supply, 16A, 16B...Power supply voltage level discrimination circuit, 1
7A, 17B...judgment circuit, 18A, 18B...gate, S
PA, SPB...power supply voltage level display signal, SGA, SG
B...Gate signal■

Claims (1)

[Claims] 1. In a signal transmission method in a device A and a device B that mutually exchange signals and are each driven by separate power supplies, each of the devices A and B indicates that the power source is at a normal voltage level or higher. Generates a power supply voltage level display signal consisting of a logic "1" or a logic "0" indicating that the voltage is below the normal voltage level, and receives the power supply voltage level display signal from the device A or device B of the other party. and monitor the device A and device B.
one device accepts the signal from the other device after confirming that the power supply voltage level display signal from the other device continues to generate logic “1” for a predetermined period; A signal transmission method characterized in that when the power supply voltage level display signal generates logic "0", reception of a signal from the other device is immediately stopped.