JPS60211553A - Input/output circuit of microcomputer - Google Patents

Abstract

PURPOSE:To attain the mixed use of inputs/outputs in one port by providing two kinds of registers in the unit of ports and bits, an output inhibition register and an output driver. CONSTITUTION:A control register 1 is a register deciding the floating in the unit of ports and a port 6 is controlled by one bit. The output inhibition gate 2 outputs an L level to a signal 3 when an output of the control register 1 is at L level and outputs a DRIVE 1 signal 5 to the signal 3 when the level is at the H level. The output driver 4 consists of 8 drivers and 8 input/output terminals of the port 6 are driven by the control of the signal 3. Thus, all the input and output terminals of the port 6 are brought into the floating state by writing ''0'' to a bit corresponding to the port 6 of the control register 1 and the data is outputted while the DRIVE 1 signal 5 is at H level by writing ''1''. This is applied similarly to other ports except that bits corresponding to the control register are different.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a microcomputer 2i with a 0MO8 configuration.
−:” This is related to the input/output circuit.

Conventional configuration and its problems In microcomputer LSI with 0MO3 configuration,
In order to achieve low power consumption, it is necessary to keep the input/output terminals in a floating state except when outputting.

Conventionally, this floating control of input/output terminals has been performed either on a port-by-port basis or on a bit-by-bit basis. However, for floating control on a port-by-port basis, 1
The drawback was that detailed control was not possible when input and output coexisted within a port.

In addition, bit-by-bit control requires a control circuit that corresponds to all input/output terminals, and even though that circuit is extremely large, bit-by-bit control among all input/output terminals is required. The disadvantage is that only a few terminals are required.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks of the conventional technology, and allows input and output to be mixed within one port with a slight increase in circuitry compared to a floating control circuit for each port. The purpose of the present invention is to provide a microcomputer input/output circuit that can be used as a microcomputer.

Structure of the Invention The present invention S1: Floating of input/output terminals is determined by using a port, which is a collection of several input/output terminals, as a unit.
1 at the output of the first register.
; a first gate that prohibits output on a port-by-port basis;
First game! 11i power: A first output driver that is turned on and off in units of 1 baud, a second register that determines the bit-by-bit floating of the input/output terminal, and a bit that is turned on and off by the output of the second register. This is a microcomputer input/output capo-1 circuit that is equipped with a second gate that inhibits unit output, and a second output driver that is turned on and off in bit units by the output of the second gate. An input/output terminal that can switch input/output and an input/output terminal that can switch input/output in bit units can be mixed on one microcomputer.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

In this example, input/output terminals are assigned to ports in 8-bit units)
-(8), ports 1 to 8 control the 70-tings of their respective input/output terminals on a boat-by-boat basis, and port (0) on a bit-by-bit basis.

FIG. 1 shows a block diagram of the input/output circuit of port (1). Control register 1 is a register that determines floating on a port-by-port basis, and controls port (1) with its 1 bit. The output inhibit gate 2 outputs a low level signal 3 when the output of the control register 1 is low level, and outputs a DRIVE1 signal 5 as a signal 3 when the output is high level.

The output driver 4 is composed of eight drivers 41 to 48 as shown in FIG. 3, and drives the eight input/output terminals of the port 1 under the control of the signal 3.

Each driver is connected to an input/output terminal as shown in FIG. 5, and when signal 3 is low level, E signal 27 is low level, E signal 28 is high level, and N channel M
O8) U5 The register 32 and the P-channel MO3I transistor 29 are both turned off, and the input/output terminal 33 returns to the floating state. When the signal 3 is at the no-y level, the E signal 27 becomes high level and the E signal 28 becomes low level, turning on both transistors and outputting data to the input/output terminal. Therefore, port 6 of control register 1) corresponding to B,+
By writing 0'' to the port (1), all input/output terminals of port (1) become floating, and 8-bit data can be input by setting the pass line (control signal 10 of 8) to the blank level. , '1'' while the DRIVE1 signal 6 is at the 71-level level.
Bit data can be output. Note that the port (
When 1vj is added to 2) to (8), the only difference is the corresponding bit of the control register, and the rest is the same as baud 1-(1).

FIG. 2 shows a block diagram of the input/output circuit of Bo)E). The control register 11 is a register that determines the 70-bit bit unit, and is different from that in FIG. 1:
, output drino (21 is 12 to 19 as shown in FIG.
The only difference is that it is controlled in units of 1゛ by the bit node 6t by 08 signals, and the other operations are the same. Therefore, by writing 0'' and 'M' to the control register 11, 1'' is written and DRIVE is performed only from the input/output terminal corresponding to the bit A7.

While the signal 22 is at a high level, data can be output, and the input/output terminal corresponding to the bit in which "o" is written can be kept floating and used as an input terminal.

In other words, by having two types of registers, one for each port and one for each bit, an output inhibit gate, and an output driver,
Ports that can switch input/output on a port-by-port basis and ports that can switch input/output on a bit-by-bit basis can coexist on one microcomputer.

Note that in this embodiment, port 1) is expressed in bit units.
Although floaty 7 is set in units of ports, the present invention has the effect of the allocation invention as described above.

The first register that determines the switching and the port J: for the output of the first register? A first gate that prohibits the output of the first gate, a first output driver that is turned on and off for each port by the output of the first gate, and a beat? a second register that determines the floating position of the bit; and a second register that inhibits the bit-by-bit output according to the output of the second register.
By equipping the output of the second gate with a second output driver that is turned on and off in bit units, only a small number of circuits are added compared to 70-bit control that uses only ports. , 111 ports can be mixed in one boat, and the port that mixes input and output is often a part of the overall input and output terminals, and is extremely advantageous in practice.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the input/output circuit of port (1) according to an embodiment of the present invention, Fig. 2 is a block diagram of the input/output circuit of port (1) of the same embodiment, and Fig. 3 is a block diagram of the input/output circuit of port (1) of the same embodiment. FIG. 4 is a logic circuit diagram of the 20th output driver, and FIG. 5 is a MO8 circuit diagram of the portion connected to the input/output terminal of the driver. 1...First register, 2...First gate, 4...First output driver, 11...
River/Second register, 20...Second gate,
21... Second output driver, 29, 30...
...P channel MOS) transistor, 31.32.
...N channel MOS) transistor, 33...
...Input/output terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 5 Procedural amendment document June 1985 (lj 1) 1 Indication of the case 1986 1.1 Patent application No. 69344 2 Name of the invention Microcomputer input/output circuit 3 Person making the correction 1'1 Occupation Application for permission
People (1: i!Ii Oaza Baru 1'', Kadoma City, Osaka Prefecture (100
No. 6 No. 4 Agent 571 Address Matsushita Electric Industrial Co., Ltd. 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture 6 Detailed description of the invention in the specification subject to amendment 6 Drawing 6 Contents of amendment (1) Description 4 Correct "Ports 1 to 8" on the 4th line of the page to "Ports (1) to (8)". (2) Correct "Port 1" on lines 15-16 of page 4 of the statement to "Port (1)". (3) “Ports 1 to 7” on page 6 of the statement, lines 15 to 16
” to “port (1) to (force)”. (4) Correct the 1-bit unit on the 6th line of page 7 of the specification to “bit unit”. (5) Drawings Figure 5 is corrected as shown in the attached drawing. Figure 5 E-1Z Vo.

Claims (1)

[Claims] A set of several input/output terminals is defined as one port, and there is a first register that determines the 70-timing of each port, and a first register that prohibits output of each port by the output of this first register. gate, and a first gate that is turned on and off for each port by the output of this first gate.
This second gate includes an output driver, a second register that determines bit-wise 70-ting of the input/output terminal, and a second gate that inhibits bit-wise output by the output of this second register. An input/output circuit for a microcomputer, characterized in that it has a second output driver that is turned on and off in bits by the output of the microcomputer.