JPS6031641A - One chip microcomputer - Google Patents

Abstract

PURPOSE:To simplify the constitution of an external circuit at the mounting of the chip by switching and selecting designated modes and modes enabled to be set up from the external by the value of one externally connected pin. CONSTITUTION:Microprogrammable mode registers 13a-13c setting up mode data designated by the user are formed on a semiconductor chip 10. The modes set up by the registers 13a-13c and the modes enabled to be set up from the external are switched and selected by the value of one externally connected pin 17. Therefore, an optional mode can be set up without a specific external circuit to be connected by the user or unconscious of a specific program mode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a one-chip microcomputer with improved mode setting functions including user-specified modes.

Central processing unit (CPU), read-only memory (RO)
A so-called one-chip microcomputer has been realized in which a random access memory (RAM), an input/output capacitor (Ilo; 1e-)), etc. are housed in the same semiconductor chip. Such one-chip microcomputers do not perform arithmetic processing using only the built-in ROM and RAM, but instead use the external connection bin assigned as the I10 port as a data transmission path connection terminal to connect external It has the ability to connect expansion ROM, RAM, etc. Furthermore, X/No. 6? −
In order to realize functions that expand the number of modes, it is equipped with a mode setting function that allows you to select and set any mode from among multiple modes. In reality, approximately eight types of modes are required in consideration of cases such as testing this chip.

For example, these eight types of modes are classified depending on whether the internal memory is normally accessed or the external memory is accessed. The following methods are known as means for selecting and setting any one mode from among these eight modes P.

First, there is a means of using three connection bins to import externally set mode setting information into the chip at the time of reset, and to set the mode. In this case, if the three pins mentioned above are assigned, for example, to be specific to mode specification, not only will the number of external connection pins increase, but also a large amount of connection pins will be wasted, causing a reduction in the functions within the chip. Become. Therefore, the connection bin for importing the external setting mode is shared with other functional pins.

However, in a one-chip microcomputer with such functions, many external circuits must be provided around the external connection bins on the board in which this chip is mounted. Therefore, the peripheral circuitry becomes extremely complicated, requiring many circuit parts when mounting the chip, and various problems remain in terms of mounting cost, noise resistance, and reliability.

Also, as a second means, by external terminal I/IE,
It is conceivable to switch whether the program after reset is based on an internal ROM or an external ROM, and to set the mode in the program executed after reset. However, with such a program, it is troublesome for the user to be aware of the mode in the program.

This invention was made in view of the above points, and it not only makes it possible to use external connections sufficiently efficiently, but also simplifies the external circuit configuration at the time of mounting and provides sufficient reliability. A one-chip microcomputer that allows users to use it easily.
The aim is to provide data.

That is, the one-chip microcomputer according to the present invention has a mask programmable mode register in the semiconductor chip for setting mode data specified by the user, and can distinguish between the mode set in this register and a mode that cannot be set from the outside. are switched and selected depending on the value of one external connection bin.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows its configuration. First, three external connection pins 11&+11b111c are provided on a semiconductor chip 1° constituting a microcomputer.
~llc are connected to the D input terminals of latch circuits 12h, 12b, and 12c each constituted by a D-type frizzo flop via a signal line. Also, this connection bin l
la to lle are connected to the I10 port not shown in the figure.

This chip 10 has a mask programmable mode register 13m which sets and outputs mode data designated by the user and programmed by a mask.
, 13b, 13c are formed, and this register 13
Output signals from each of data selectors 6 to 13a are supplied to input terminals B of data selectors 14th, 14b, and 14c via signal lines, respectively.

In addition, a reset command (Rgsg'
r), and the signal from this pin 15 is connected to an inverter 16 and a reset signal generator, not shown. The output signal from the inverter 16 is supplied to each G input terminal of the latch circuits 12a to 12e to control the latch timing. In other words, the output of the latch circuits 12h to 12e is equal to the input when the S input is at the high (6) level, and when the S input is at the low (L) level, the G output changes from the H level to the L level. It has the function of retaining the value at the time of change. The output signals from each of the latch circuits 12a to 12a are sent to the data selectors 14 & to 14c'.
Supplied to each A input terminal.

1, the external connection bin 17 is pulled up to the power supply line via the resistor 18, and this connection bin 17 is connected to the buffer 19. The output signal from this passer 19 is supplied to the input terminal S of the data selectors 141 to 14c.
Now, when this S input is at H level, the B input is taken out as the output Y. The Y outputs of the data selectors 14h-14c are taken out as mode data signals PC0°PC, , PC,.

A one-chip microcomputer configured in this manner requires about eight types of modes to test it. In order to generate about eight types of modes, the following procedure is performed.

That is, when the RBS ET double signal is applied to the external connection bin 15, the latch circuit 1 is supplied via the inverter 16.
Signals are applied to the S inputs of the latch circuits 2h to 12c, and the latch circuits 12h to 12c take in and latch the values of the signals applied to the external connection bins lla to Ilc, respectively. Output signals corresponding to the values latched by the latch circuits 12a to 12c are set to be supplied to the A inputs of the data selectors 14a to 14c, respectively.

In this case, the signal for the external connection bin 17 is set to L level, and is applied to the data selectors 14a to 14c via the L level signal 19. Therefore, the data selectors 14a to 14c select the A input and take out the output signals from the latch circuits 12a to 12c as outputs Y, respectively, and these output signals become the set mode data signals.

In other words, if the values supplied to the external connection bins llh to llc are controlled externally when the RES ET double signal rises, the mode data signal can be controlled, and there are about 8 types of modes. can be set arbitrarily. Note that in this reset mode, the input/output port becomes an input port.

Next, the user can implement any -p-p without any external circuit as follows.

That is, the mode desired by the user is set by the mask option in the mask program/l/mode register 13&-13e according to the specification of the key f. And the data for this specified mode is
It is always supplied to the data selectors 14a to 14c.

In this case, the external connection bin 17 is in an open state,
- Since the input line to the buffer 19 is connected to the power supply via the resistor 18, the S input from the buffer 19 to the data selectors 14a to 14c is at H level. Therefore, the data selectors 14a to 14c convert the output data from the mask programmable mode renostars 13h to 13c into mode data P C6, P Cs + P C
It will be output as 2. In other words, the user-specified mode is executed.

FIG. 2 shows an embodiment in which the external connection pin 17 is also used as an output port, and a signal from this connection pin 17 is supplied to the D terminal of the latch circuit 20. Then, the output of the inverter 16 to which the RESICT signal is supplied from the external connection bin 15 is supplied to the G terminal of the latch circuit 20, and the output signal from the latch circuit 20 is supplied to the data selector as a user mode selection command. It is something to do.

That is, at the same time that the values of the external connection bins 11* to 11c are taken into the latch circuits 12h to 12e, the value of the external connection bin 17 is taken into the latch circuit 20. The output port (not shown in the figure) connected to this external connection bin 17 is set to H level (open) upon reset, and thereby the silatch circuit 20 is arbitrarily set to H level or L level. It is something that

As described above, according to the present invention, an arbitrary mode can be set without the user having to install an external circuit and without having to be particularly aware of the program mode. Moreover, it can be used as a highly reliable one-chip microcomputer.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining a one-chip microcomputer according to one embodiment of the invention, and FIG. 2 is a diagram for explaining another embodiment of the invention. DESCRIPTION OF SYMBOLS 10... Semiconductor chip, 11a-11c, 15° 17... External connection bin, 12h-12e... Latch circuit, 13a-13c... Mask programmable mode register, 14a-14c... Data selector .

Claims (1)

[Claims] A latch circuit that takes in and latches external setting mode data via an external connection bin, a mask programmable mode reno star in which mode data specified by the user is set, read mode data output from this register, and output from the latch circuit. 1. A one-chip microcomputer comprising: a data selector to which an external setting mode data output is supplied and selects one of the mode data outputs via an external connection bin.