JPS635642A - Communication control unit - Google Patents

Abstract

PURPOSE:To transmit a control signal without time lag by adding an AND circuit outputting the AND between a transmission instruction signal that a control part outputs and an NRZ signal that a reception circuit outputs and the 2nd drive circuit outputting a pulse to a line due to the output of the AND circuit to a communication control unit. CONSTITUTION:If a transistor 9 is turned on or if there is a negative pulse on a line side, a base current flows in a transistor 13, and the input port of a control part 5 and the input of the AND circuit 1 become high levels. The other input of the AN circuit 1 is connected to the output port T3 of the control part 5. By the transmission instruction signal from the control part, the output port T3 becomes a high level. If there is a pulse on the line side at that time, the both inputs of the AND circuit 1 become high levels, and the output of the AND circuit 1 instantaneously comes to a high level. The output of the AND circuit 1 is connected to the base of a transistor 8 through a resistance 17. When the output of the AND circuit 1 comes to a high level, the transistor 8 is turned on to transmit a positive pulse to the line side.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to contention during transmission between communication control units in a home bus system.

2. Description of the Related Art An embodiment of a communication control unit used in a conventional home bus system is shown in FIG. The communication control unit 18 includes a drive circuit 3 that outputs the MU signal to the line via the pulse transformer 7, a receiving circuit 4 that receives the AMI signal (bipolar RZ double signal) on the line and converts it into an NRZ signal, A control unit 6 that is connected to the receiving circuit 4 and the drive circuit 3 and controls communication according to a predetermined communication protocol.
and an interface section 6 with a higher-level terminal connected to this communication control unit 18.

FIG. 3 shows the basic format of the control signal, and FIG. 4 shows the character format. The control method is CSMA/CD method (
Carrier 5enced Multiple A
Access with Co11ision Detect
tion ), and the transmitting communication control unit detects whether the transmitted data and received data match each bit. After a collision is detected (if there is a mismatch between its own transmitted data and received data), it immediately stops transmitting and starts receiving. After that, retransmission is performed after transmission becomes possible. Due to the conflict between the priority code and the self-address part, the communication control unit with the highest priority survives.

It is determined that there is always a pause time of 10 m5 between the end of one control signal on the line and the transmission of the next control signal on the line. In other words, a communication control unit that subsequently attempts to transmit the next control signal, a communication control unit that stopped transmission due to previous collision detection and attempts to retransmit, and a communication control unit that attempts to transmit a new control signal this time, The control unit must also transmit each control signal from the priority code after a pause of 10 mg after the end of the control signal on the line.

This 10m! Since each communication control unit measures the idle time using its own timer, deviations in the crystal oscillators of each unit and timing errors in program processing occur. Therefore, in order to ensure bit contention between C8M person/CD, a recovery monitoring time T as shown in Fig. 6 is set, and the line is monitored from time T, before the end of the down time, and other Once the transmission from the communication control unit is started, it is necessary to start the transmission in synchronization with it.

Conventionally, in accordance with the flowchart shown in Figure 6, this method alternately checks for the end of a 10mS timer and monitors the start bit on the line when it is desired to transmit a control signal, and if either is recognized, transmission begins. A method using interrupt processing as shown in FIG. 8 has been devised and implemented.

Problems to be Solved by the Invention Among these conventional methods, the method shown in FIG. 6 can only monitor the start-up time on the line at every sampling time Ts, which is determined by the software processing time.
As shown in FIG. 7, if a start bit is issued to the line immediately after sampling, transmission will be delayed by the time Td until the next sampling. When the duty of the human MI waveform is 50%, the C3MA/CD method cannot be performed accurately unless this delay time is within 13 μs. In the system using interrupt processing shown in FIG. 8, it is possible to keep the delay time Td within 13 μs, but a delay of several μs is unavoidable due to the necessity of preprocessing. In this case, there is no problem with communication control, but as shown in FIG. 9, the waveform on the line becomes distorted and contains unnecessary harmonic components, which poses a problem.

Means for Solving the Problems The present invention provides an AND circuit that outputs an AND of a transmission command signal outputted by a control section and an NRZ signal outputted by a reception circuit;
A second drive circuit that outputs pulses to the line based on the output of this AND circuit is added to the communication control unit.

Effects The present invention has the above-described configuration to cause the communication control unit to transmit the control signal after the pause time without any time delay,
Bit conflicts can be ensured.

Embodiment FIG. 1 is a block diagram of a communication control unit according to an embodiment of the present invention. Note that elements common to those in FIG. 2 are given the same numbers. In FIG. 1, 1 is an AND circuit, 2 is a communication control unit, which includes an AND circuit 1, a drive circuit 3,
It consists of a receiving circuit 4, a control section 6, and an interface section 6. A pulse transformer 7 relays between the communication control unit and the line side.

8 is a transistor for outputting a positive pulse to the line side, 9 is a transistor for outputting a negative pulse to the line side, and the collector of transistor 8 is connected to one end of the primary winding of the center-tapped Kinopulse transformer 7. is connected to the other end, the collector of the transistor 9 is connected to the other end, the emitter of the transistor 8.9 is grounded, and a voltage of 5V is applied to the center tap of the pulse transformer. 1o is a resistor, which is connected to the output port T1 of the control unit 6.
The - end is connected to , and the other end is connected to the pace of transistor 8 .

Similarly, the negative end of the resistor 11 is connected to the output port T2 of the control section 6, and the other end is connected to the pace of the transistor 9. Therefore, when the output port connected to the resistor 10 of the control section 6 becomes Hi$ level, the transistor 8 turns on.
A current flows in the direction of arrow A in the primary winding of the pulse transformer 7, generates a pulse voltage in the secondary winding, and a positive pulse signal can be transmitted to the line. Similarly, when the output port connected to the resistor 11 of the control unit 5 becomes High level, the transistor 9 is turned on, and current flows in the direction of arrow A through the primary winding of the pulse transformer 7, producing a pulse voltage in the secondary winding. A negative pulse signal can be sent to the line side. Reference numerals 12 and 13 designate transistors, the emitter and transmitter of which are connected to the input port of the control unit 5 and the input of the AND circuit, and the collector of which is connected to 6V. 1
4 is a resistor, one end of which is connected to the pace of the transistor 12, and the other end of which is connected to one end of the primary winding of the pulse transformer 7. The other end of the pulse transformer is connected to one end of a resistor 15, and the other end of the resistor 15 is connected to the pace of the transistor 13. 16 is a pull-down resistor. When the transistor 8 is turned on, or when there is a positive pulse on the line, a pace current flows through the transistor 12, the transistor 12 is turned on, a collector current flows through the resistor 16, and the voltage drop causes the control section 5 to The input port and the input of the AND circuit 1 are set to High level. Also, when the transistor 9 is turned on or when there is a negative pulse on the line side, a pace current flows through the transistor 13, and the input port of the control unit 6 and the input of the AND circuit 1 go high.
h level.

Another input of the AND circuit 1 is connected to the output port T of the control section 6. At the output port, 3 becomes High level due to the transmission command signal of the control unit, and if there is a pulse on the line side at this time, both inputs of AND circuit 1 become High.
becomes high level, and the output of AND circuit 1 instantly goes high.
gh level.

The output of the AND circuit 1 is connected to the transistor 8 via the resistor 17.
is connected to the pace of , and the output of AND circuit 1 is Hi
When it reaches the gh level, the transistor 8 turns on and sends a positive pulse to the line side. That is, if a pulse comes on the line while the control section is issuing a transmission command, the communication control unit that receives the pulse can instantaneously send a positive pulse onto the line.

Effects of the Invention As described above, according to the present invention, control signals for communication control can be transmitted without time delay.
Bit contention can be ensured.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a communication control unit in an embodiment of the present invention, Fig. 2 is an explanatory diagram of conventional communication control unit interrogation and recovery monitoring time, Fig. 6 is a flowchart of conventional communication control, and Fig. 7 is a schematic diagram of data of delay time Td. 1...Logic product circuit, 2...Communication control unit, 3...Drive circuit, 4...
Receiving circuit, 5...control section, 6...interface section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Communication Control Unit Figure 2/8'' Candy I West Unit Figure 3 (Note): See (Xvr) Figure 4 Each bit is transmitted from the LSB (negative logic). LSB data MSB
Stop (1 bit) Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] a pulse transformer that connects the line and the communication control unit; a first drive circuit that outputs the bipolar RZ signal to the line; a receiving circuit that receives the bipolar RZ signal on the line and converts it into an NRZ signal; a control unit connected to the receiving circuit and the drive circuit and controlling communication according to a predetermined communication protocol; an interface unit connected to the communication control unit with a higher-level terminal; a transmission command signal outputted by the control unit; A communication control unit comprising an AND circuit that outputs an AND with an NRZ signal output by a receiving circuit, and a second drive circuit that outputs a pulse to a line based on the output of the AND circuit.