JPH0430058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides an output interface circuit that allows multifunctional output terminals and does not result in an increase in the number of output terminals. The present invention relates to a large-scale integrated circuit configured as a built-in device.

Conventional configurations and their problems In recent years, large-scale integrated circuits (LSIs) have become more multifunctional and highly integrated, and the number of output terminals per LSI (one chip) has tended to increase. This increase in the number of output terminals results in an increase in the area of the semiconductor substrate constituting the LSI, an increase in the size of the sealing structure, and an inconvenience that increases the price of the LSI. In order to eliminate this inconvenience, it would be sufficient to reduce the number of output pins, but the multifunctionality and high integration of LSIs described above bring about changes in LSIs that are contrary to this reduction in the number of output pins. ing.

Incidentally, the increase in the number of output terminals due to multifunctionalization and high integration is mainly caused by the configuration of circuit sections that function to extract various signal outputs.

Figure 1 shows the integrated LSI, for example,
1 is a block diagram showing a conventional example of a circuit section that operates to extract two types of signal outputs; FIG.

As shown in the figure, this circuit section is composed of a decoder section 2 directly connected to the data bus 1 that outputs a plurality of data of the internal circuit, and latch sections 3, 31, and 32 connected to the decoder section 2 and the internal data bus 1. Furthermore, each latch portion 3, 31, 32 is connected to an output port 4, 41, 42. Although such a circuit has a simple configuration and can be said to be simple, the number of output terminals inevitably increases because the circuit configuration is such that various signals are output to separate output ports. Therefore, with such a configuration of the circuit section, it has not been possible to prevent the product price from rising due to an increase in the number of terminals.

Purpose of the Invention The present invention has a built-in interface circuit that can output a plurality of data signals selected from a variety of data signals from the same terminal as a group in order to extract various signal outputs, and an LSI with multiple functions. The object of the present invention is to provide an LSI whose number of output terminals does not increase even when the number of output terminals increases even when the number of output terminals increases.

Structure of the Invention The large-scale integrated circuit of the present invention has a data bus for transmitting a plurality of data in an internal circuit, and a data bus for transmitting a plurality of data in an internal circuit, in order to output a plurality of data selected from a variety of data signals to an output terminal as a group. a decoder section that receives data from and converts the data; a multiplexer section that inputs a plurality of data from the data bus and the converted data from the decoder section and selects one of them; and a data selection of the multiplexer section. a gate circuit that emits a signal to control the
The configuration includes a latch section for latch-controlling the output of the multiplexer, and an output port connected to the latch section. With this configuration, 1
One output terminal is common to one group of data.

DESCRIPTION OF EMBODIMENTS A large-scale integrated circuit of the present invention will be described with reference to FIG.

FIG. 2 is a diagram showing an embodiment in which an output interface circuit of a 1-chip 4-bit microcomputer, which is one of large-scale integrated circuits, has a circuit configuration according to the present invention. Decoder 6 inputs data on data bus 1, converts the data, and outputs the data to multiplexers 7 and 71. The decoder 6 has an auxiliary signal input terminal 5, and is controlled by an auxiliary input signal applied thereto from the outside. The multiplexers 7 and 71 each input the converted data from the decoder and the data from the data bus 1,
Select one and output. The outputs of multiplexers 7 and 71 are transmitted to output ports 43 and 44 via latches 33 and 34, respectively.

By the way, the basic operation of this interface circuit is as follows.

The data on the data bus 1 and the auxiliary input signal applied to the auxiliary signal input terminal 5 are always input to a decoder 6, and the data on the data bus is converted into 8-bit data by the decoder 6. A switching control signal issued by the gate circuit 8 in response to a signal from the outside or within the integrated circuit selects whether to select the bus data or the decoder output.

In addition, the latches 33 and 34 are latch-controlled by signals generated by the gate circuits 10 and 11 in response to the output of the gate circuit 8 and control signals applied from the outside to the output control signal application terminals 9 and 91, respectively. , taken out to output ports 43 and 44.

In the large-scale integrated circuit of the present invention configured as described above, the output port can be used in two ways.

That is, one method is to use each as an independent output port and output the contents of the data bus as is. The other method is to combine two output ports into one, use a decoder to convert from 4 bits to 8 bits, and output this converted data at once to create an 8-bit output port. It is.

Effects of the Invention As explained above, the large-scale integrated circuit of the present invention suppresses the increase in the number of output terminals due to multi-functionality and high integration, and the increase in the number of output terminals causes the price to rise. Inconveniences can be eliminated.

Furthermore, when the configuration of a general-purpose one-chip microcomputer is adapted to the configuration of the large-scale integrated circuit of the present invention, when the user selects the output terminal, it becomes possible to make this selection on the program. This also has the effect of realizing a microcomputer that is easy to use.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a data output circuit section of a conventional large-scale integrated circuit with improved output terminal functions, and FIG. 2 is a diagram showing the configuration of a data output circuit section of a large-scale integrated circuit according to the present invention. FIG. 1...Data bus, 2, 6...Decoder, 3,
31-34...Latch, 4,41-44...Output port, 5...Auxiliary signal input terminal, 7,71...
Multiplexer, 8... Gate circuit for multiplexer switching signal generation, 9, 91... Output control signal application terminal, 10, 11... Gate circuit for output control signal supply.

Claims (1)

[Scope of Claims] 1. A data bus that transmits a plurality of data of an internal circuit; a decoder unit that receives data from the data bus and converts the data; and a data bus that transmits a plurality of data from the data bus and the decoder unit. a multiplexer section that inputs converted data and selects one of them; a gate circuit that issues a signal that controls the data selection of the multiplexer section; a latch section that latches the output of the multiplexer; large scale integrated circuit with output ports.