JP2889309B2 - Terminal circuit of multiplex transmission system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a terminal circuit of a multiplex transmission system, and is used, for example, for a terminal IC of a time division multiplex transmission system.

2. Description of the Related Art Conventionally, a multiplex transmission system in which one master unit and a plurality of terminal circuits are connected to a common transmission line, and control data is transmitted from the master unit to each terminal circuit by a multiplex transmission method has been widely used. ing. A multiplex transmission signal having a transmission start signal, an address signal, a control signal, a reply standby signal, and a transmission end signal as one frame is transmitted from the master unit to the terminal circuit. The terminal circuit includes a multiplex transmission circuit for receiving and decoding the multiplex transmission signal. If the address signal matches the address of the own station, the terminal circuit reads the control data included in the control signal, Is returned in synchronization with the response standby signal.

[Problems to be Solved by the Invention] By the way, in a terminal circuit, it is necessary to sound a buzzer to generate an alarm sound or a notification sound, or to generate an acoustic signal to transmit a call sign (identification sound). There are cases. If this kind of alarm sound, notification sound, and identification sound cannot be represented by a single scale, it is necessary to generate a plurality of acoustic signals having different scales. Conventionally, in order to generate such a plurality of acoustic signals, a circuit for voice modulation is required, and there has been a problem that the circuit configuration is complicated.

The present invention has been made in view of such a point,
An object of the present invention is to provide a terminal circuit of a multiplex transmission system capable of generating a plurality of acoustic signals without using a circuit for voice modulation.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, as shown in FIG. 1, control data is received from a master unit via a transmission line of a multiplex transmission system. An oscillation frequency is determined by a multiplex transmission circuit 3 and a time constant of a capacitor and a resistor. The CR oscillation circuit supplies an operation clock to the multiplex transmission circuit 3 and outputs the clock to the outside as an acoustic signal via an oscillation output terminal φ. 1, an analog switch SWi for adjusting the resistance value, a non-volatile memory 2 such as an E ² PROM for storing the adjustment result of the resistance value by the analog switch SWi, and the multiplex transmission circuit 3 And a data setting circuit 4 for writing control data to the nonvolatile memory 2.

[Operation] According to the present invention, as described above, the value of the time constant setting resistor in the CR oscillation circuit 1 that generates an acoustic signal can be adjusted by the analog switch SWi, and the adjustment result is stored in the nonvolatile memory 2. Since the information is stored, a plurality of acoustic signals can be generated. The control data received by the multiplex transmission circuit 3 is transmitted to the data setting circuit 4.
Thus, the sound signal generated on the terminal circuit side can be modulated by remote control from the master unit.

Embodiment FIG. 1 is a block circuit diagram of one embodiment of the present invention.
This circuit shows the internal configuration of the terminal IC 5 for time division multiplex transmission, and includes a multiplex transmission circuit 3 for controlling for time division multiplex transmission, and a CR oscillation circuit 1 for supplying an operation clock thereto. , And an analog switch SWi and an E ² PROM ² for adjusting the oscillation frequency.

The multiplex transmission circuit 3 operates by the clock oscillated by the CR oscillation circuit 1, performs time-division multiplex transmission with the master unit connected to the transmission line Q, and transmits input data from the input / output port P to the master unit. And a control signal is output from the input / output port P under the control of the master unit. The value of the resistor for setting the time constant of the CR oscillation circuit 1 is determined by the analog switch SW.
i can be changed freely. The analog switch SWi is controlled to an on state or an off state based on data in the E ² PROM ² .

FIG. 2 shows a specific circuit configuration for adjusting the value of the time constant setting resistor in the CR oscillation circuit 1. E ² PROM2
The data D ₁ to D ₅ on the bus is written by the write signal WR. The analog switch SW ₁ to SW ₅ corresponding to each bit of the E ² PROM 2 stored in the data D ₁ to D ₅ are controlled to be on or off state. When any one of the analog switches SWi (i = 1 to 5) is in the ON state, the resistor Ri corresponding to the switch SWi is short-circuited, and the resistance between the terminals A and B is reduced by the short-circuited resistance. Becomes smaller. For example, data D ₁ , D ₂ , D ₃ , D ₄ , D ₅ stored in the E ² PROM ₂
Are 0, 0, ₁ , ₁ , ₁ , the switches SW ₁ and SW ₂ are turned off, and the switches SW ₃ , SW ₄ and SW ₅ are turned on. Thus, the resistance between the terminals A and B becomes r ₀ + R ₁ + R ₂ . With the above method, writing data to E ² PROM ²
A, the resistance between the B can be freely changed by the combination of R ₀ to R _5. That is, the oscillation frequency of the CR oscillation circuit 1 can be adjusted.

In this embodiment, in order to generate an acoustic signal,
A clock generated by the CR oscillation circuit 1 is extracted from an oscillation output terminal φ, and is input to a speaker 7 via an amplifier 6. This constitutes an electronic buzzer. To make the electronic buzzer sound, the amplifier control signal S is taken out from the input / output port P and given to the amplifier 6. Further, when changing the scale of the electronic buzzer, after setting the data for designating the musical scale in the data setting circuit 4 from the multiplex transmission circuit 3, by generating a write signal WR shown in Fig. 2, E ² PROM 2 Just write the data to

Note that terminal ICs for time-division multiplexing often include an E ² PROM for setting the address of the own station, and a part of the storage area of the E ² PROM is used for storing the resistance value adjustment data. It may be diverted as a storage area.

According to the present invention, as described above, the value of the time constant setting resistor in the CR oscillation circuit can be adjusted by the analog switch and the nonvolatile memory, and the control data received by the multiplex transmission circuit can be adjusted. Can be written into the non-volatile memory by the data setting circuit, so that a plurality of acoustic signals can be generated by remote control without using an audio modulation circuit. In addition, since the CR oscillation circuit that generates the acoustic signal is also used as the oscillation circuit of the operation clock of the multiplex transmission circuit, there is no need to newly provide a sound source, and there is an advantage that it can be configured at low cost.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention, and FIG. 2 is a main part circuit diagram of the embodiment. 1 is a CR oscillation circuit, 2 is a nonvolatile memory, 3 is a multiplex transmission circuit, 4 is a data setting circuit, and SWi is an analog switch.

Continuation of the front page (56) References JP-A-64-86708 (JP, A) JP-A-53-76785 (JP, A) "Handbook of practical electronic circuits (3)" (Transistor technology editorial department, CQ Publishing Co., Ltd.) (Company) P136-137 (58) Field surveyed (Int. Cl. ⁶ , DB name) G08B 23/00-27/00 G10K 9/12 104

Claims (1)

(57) [Claims] An oscillation frequency is determined by a multiplex transmission circuit for receiving control data from a master unit via a transmission line of a multiplex transmission system, and a time constant of a capacitor and a resistor. A CR oscillation circuit that externally outputs the clock as an acoustic signal via an oscillation output terminal, an analog switch for adjusting the value of the resistor, and a non-volatile memory that stores a result of adjustment of the value of the resistor by the analog switch. A data setting circuit for writing control data received by the multiplex transmission circuit into the nonvolatile memory.