JPH0358205A - Microcomputer - Google Patents

Abstract

PURPOSE:To shorten the restart time of a prescribed operation by detecting the fluctuation of a source voltage set at an operation stopping state, and preserving the content of a memory register, etc., without initializing when no source voltage goes less than a constant voltage while the operation stopping state is set. CONSTITUTION:A microcomputer makes a source voltage fluctuation detection circuit 2 monitor the fluctuation of the source voltage after interrupting the execution of a program instruction with a stopping signal. When a state is shifted from a stopping state to an operating state, a data setting signal 11 on a program counter 12 is generated. When the state is shifted to the operating state without setting the source voltage fluctuation detection circuit 2 at this time, data setting on the program counter is prohibited with AND gates 9 and 10 even when the data setting signal 11 on the program counter 12 is generated, thereby, the content of the program counter is held. In such a way, a time required for the start of the prescribed operation can be reduced.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a microcomputer.

[Prior Art] Conventionally, when the power supply voltage drops below a predetermined voltage during a period when a microcomputer is not operating, the state of data pits held in a built-in memory register or the like becomes undefined. On the other hand, if the power supply voltage is maintained at a predetermined voltage or higher, data pits in built-in memory registers, etc. are stably held. As mentioned above, in conventional microcomputers, although the data in registers etc. can be in one of two states depending on the power supply voltage, when transitioning from the stopped state to the operating state, it is necessary to check whether or not there is a change in the power supply voltage used. Memory registers etc. were always initialized regardless of the situation.

[Problems to be solved by the invention] In conventional circuits, all the states of memory registers etc. are initialized when transitioning from a stopped state to an operating state, so it is necessary to reset the states necessary for operation by a program. This has disadvantages in that the program becomes long and it takes a long time to start a predetermined operation.

[Differences between the invention and the prior art] In contrast to the above-mentioned conventional circuits, the present invention is capable of immediately starting a program without initializing memory registers, etc., if the power supply voltage does not drop below a specified voltage during the operation stop period. The difference is that it is possible to shift to a predetermined operating state quickly.

[Means for solving the problem] The gist of the present invention is to suspend execution of the program instruction in response to a stop signal during execution of the program instruction, and resume execution of the program instruction after the stop signal is released. In a microcomputer, data holding means holds data codes necessary for executing program instructions, and monitors fluctuations in power supply voltage while suspending execution of program instructions, and stores fluctuations in power supply voltage when such fluctuations occur. Determines whether or not to reset the data code in the data holding means in response to the power supply voltage fluctuation detection circuit and a control signal indicating the presence or absence of the power supply voltage output from the power supply voltage fluctuation detection circuit when the program instruction is restarted. and has a data resetting means for executing the data resetting.

[Operation of the Invention] After the above-mentioned microcomputer interrupts the execution of the program instruction by the stop signal, it causes the power supply voltage fluctuation detection circuit to monitor fluctuations in the power supply voltage. If there is a change, the data resetting means resets the data code necessary to execute the program command after the stop signal is released, and if there is no change, the program command is executed without resetting the data code. resume.

[Example code] Next, one embodiment of the present invention will be described with reference to FIG.

In Fig. 1, 1 is the power supply, and 2 is the operation stop state when the power supply voltage drops below a certain voltage (state B in Fig. 2), and then when the power supply voltage is restored (state C in Fig. 2). Each figure shows a power supply voltage fluctuation detection circuit that is always set in one direction.

This flip-flop 2 will be explained in detail below.

Reference numeral 3 indicates a P-type enhancement type transistor, 4 indicates an N-type enhancement type transistor, and 5 indicates an in-J signal, which is at a high level in the operating state (state E in FIG. 9). When the power supply voltage is the same voltage as in the operating state in the stopped state (state A in Figure 2), 3 and 4 become conductive, but due to the resistance ratio of 3 and 4, a high level is output to the contact N of 3 and 4. , 5 are at low level, and the output of 6 is also at low level. If the power supply voltage drops below the constant voltage determined by the resistance ratio of 3 and 4 in the stopped state (state B in Figure 2), the human power of 5 becomes low level and the output of 6 becomes high level (this state is changed to 2). is set).

For the convenience of the following explanation, a program counter consisting of a 12-bit flip-flop is capable of adding and subtracting its own value, and the value can be set by external data. It is assumed that the flow of processing can be instructed by sequentially instructing a memory (not shown) that stores the program. 9 and 10 are AND gates, and 11 is the state of E for setting data to the program counter 12), and a data setting signal l1 to the program counter 12 is generated. At this time, the power supply voltage fluctuation detection circuit 2
is set, the program counter 12 is set to OOH by the AND gates 9 and 10 and the data setting signal 11, and the program is executed from 00H. If the flip-flop 2 is not set to the operating state, the program counter 12
Even if data setting signal 11 is generated, data setting to the program counter is prohibited by AND gates 9 and 10, the contents of the program counter are held, and processing can be resumed according to the contents, and special No additional program processing is required.

In the above embodiment, the &games 9 and 10 constitute the data resetting means 100.

[Effects of the Invention] As explained above, the present invention detects fluctuations in the power supply voltage during the operation stop state, and if the power supply voltage does not drop below a certain voltage during the operation stop state, the memory register, etc. By saving the contents without initializing them, there is no need to reset the contents of memory registers, etc. by program when transitioning from a stopped state to an operating state, which has the effect of reducing the time required to resume the desired operation. be.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing fluctuations in power supply voltage, and FIG. 3 is a waveform chart of signals showing transition from a stopped state to an operating state. 1... Power supply, 2... Power supply voltage fluctuation detection circuit, 3... P-type enhancement transistor, 4...
...N-type enhancement transistor, 5...
...Inverter, 6...R-S flip-flop, 7...Reset signal for resetting 2 immediately after power is turned on, 8...Indicates transition between stop state and operating state. signal, 9,
10...AND gate, 11...Program counter data setting signal, 12
...Program counter.

Claims (1)

[Scope of Claims] A microcomputer that interrupts execution of the program instruction in response to a stop signal during execution of the program instruction, and resumes execution of the program instruction after the stop signal is released, comprising: a data holding means for holding a data code; a power supply voltage fluctuation detection circuit for monitoring power supply voltage fluctuations while the execution of a program instruction is interrupted and storing the fluctuations in the power supply voltage at the time of the fluctuation; It has data resetting means for determining whether or not to reset the data code in the data holding means in response to a control signal indicating the presence or absence of the power supply voltage output from the power supply voltage fluctuation detection circuit at the time of restart. A microcomputer characterized by: