JPH03192934A - Response signal sampling method - Google Patents

Abstract

PURPOSE:To improve the reliability by sampling a response signal even in a 2nd sample timing when a prescribed response signal cannot be sampled in a 1st sample timing. CONSTITUTION:When a prescribed response signal to be sampled at first cannot be sampled in a sample timing P1, the generating period of a timing signal TX is extended and a 2nd sample timing P2 delayed by a prescribed time with respect to the sample timing P1 is decided. Then the response signal is sampled even in the 2nd sample timing P2. Thus, sure sampling of the response signal is attained and the reliability is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention sends a periodically generated timing signal to a slave station, and responds to the response signal that is returned from the slave station in response to the timing signal. The present invention relates to a response signal sampling method for sampling at a sample timing delayed by a predetermined time with respect to a timing signal.

[Conventional technology]

Conventionally, as shown in FIG. 2, communication interfaces 2-1 to 2-L, which serve as slave stations, are connected to a transmission path extending from a master station 1.
are connected to each of these communication interfaces 2-1 to 2-1.
A communication system is known in which information sent in 2-h is returned in response to a transmission request from the master station 1.

Communication interface 2-t~2. ,． 1 is a sensor section 2 such as a temperature sensor, humidity sensor, smoke sensor, security sensor, etc.
-0 to 2-1 and driver/receiver sections 2-12 to 2-.
．． t, uses the information detected by the sensor units 2-8 to 2-0 as response data, and returns this response data in response to a transmission request from the master station 1.

In FIG. 3(a), the master station 1 uses communication interfaces 2 to 2-.
This timing signal TX is generated at a predetermined period T. That is, the communication interface specified by the master station 1 returns each bit of the response data as a response signal to the master station 1 at every falling edge of the periodically generated and sent timing signal TX. The master station 1 receives response data from the communication interface as reception data RX (Fig. 3(b)), and changes the level of each bit of this reception data RX, that is, the level of each response signal, to its timing signal T.
Sampling is performed at a sample timing Pl delayed by a predetermined time t1 with respect to the falling edge of X.

[Problem to be solved by the invention]

However, according to such conventional sampling methods, for example, a specified communication interface and a master station
If the transmission distance between the main station 1 and the main station 1 is long, the response signal to the master station 1 may be input with a large delay, as shown by the dashed line in FIG. 3(b). In such a case, the master station I cannot sample the level of the response signal at the normal sampling timing P, resulting in a decrease in reliability.

[Means to solve the problem]

The present invention has been made to solve such problems, and when a predetermined response signal that should be sampled first cannot be sampled at sample timing P, the generation of timing signal TX is In addition to extending the period, a second sample timing P delayed by a predetermined time with respect to the sample timing Pl is determined.
The response signal is also sampled at the sample timing PR.

[Effect]

Therefore, according to the present invention, if, for example, the start bit cannot be sampled as a predetermined response signal to be sampled first, the generation period of the timing signal TX is lengthened and the first sample timing P, In addition, the response signal is sampled at the second sampling timing P.

〔Example〕

Hereinafter, the response signal sampling method according to the present invention will be explained in detail.

FIG. 1 (al and ka) is a time chart for explaining one embodiment of this response signal sampling method,
This corresponds to FIGS. 3(a) and ib) shown as the conventional method.

That is, it is assumed that the transmission distance between the designated communication interface and the master station is long, and a response signal to the master station is input with a large delay. In this case, the master station attempts to sample the rlJ level start bit (#ST) as a predetermined response signal to be sampled first at the normal sampling timing pt (38 points shown in FIG. 3). However, since the response signal to the master station is input with a long delay, the normal sample timing P
+, the start bit cannot be detected.

In this case, the master station extends the generation period of the timing signal TX to T2, and also sets a second sample timing Pg delayed by a predetermined time t with respect to the normal sample timing P+ (see Figure 3). point), and this second sample timing P! However, in this embodiment, the normal generation period TI of the timing signal TX is assumed to be 1 bit, and this 1 bit is extended by half a bit to obtain the generation period T.
It is set at 2. In addition, the second sample timing P is a time point delayed by half a bit with respect to the sample timing P.
! has been established.

That is, according to the sampling method according to this embodiment,
The rHJ level start bit is detected at the second sample timing P8, and thereafter, T! Based on the timing signal TX with the generation period, the normal sample timing P
, the response signal is sampled at the second sampling timing Pg in addition to , and the logical sum of the sampling level at sample timing P and the sampling level at sample timing P1 is adopted as the correct sampling level. Even if a response signal is input with a large delay, the response signal can be reliably sampled, and its reliability is greatly improved compared to conventional methods.

Note that if the start bit cannot be detected at the first sample timing PI, the second sample timing P2
The sampling level of the response signal at P1 may be always adopted as the correct one, but by calculating the logical sum with the sampling level at sample timing P1, for example, if the input delay of the response signal is recovered midway, Also, even if the delay in the input of the response signal is a slight delay before and after the sample timings P and P2, reliable and accurate sampling results can be obtained.

〔Effect of the invention〕

As explained above, according to the response signal sampling method according to the present invention, a predetermined response signal to be sampled first is sampled at the sample timing P.

If it is not possible to sample at
In addition to extending the generation period of the timing signal TX, a second sample timing P8 is set that is delayed by a predetermined time with respect to the sample timing P, and the response signal is sampled at this second sample timing pg as well. It becomes possible to reliably sample the response signal, and its reliability is greatly improved compared to conventional methods.

[Brief explanation of drawings]

FIG. 1 is a time chart showing the relationship between the timing signal TX and the received data RX to explain an embodiment of the response signal sampling method according to the present invention, and FIG. 2 is a time chart showing the relationship between the timing signal TX and the received data RX, and FIG. FIG. 3 is a time chart showing the relationship between timing signal TX and received data RX to explain the conventional response signal sampling method. It is.

Claims (1)

[Claims] A response signal sampling method in which a periodically generated timing signal is sent to a slave station, and a response signal prompted by the timing signal and returned from the slave station is sampled at a sample timing delayed by a predetermined time with respect to the timing signal. In this case, if the predetermined response signal that should be sampled first cannot be sampled at the sample timing, the generation cycle of the timing signal is lengthened, and the second response signal delayed by a predetermined time with respect to the sample timing is Determine the sample timing of
A response signal sampling method characterized in that the response signal is sampled at this second sampling timing as well.