JPH0247919A - Semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To facilitate the change of the driving capability of the device by constituting the final stage of an output circuit driving an external circuit with plural number of transistors(TRs) and changing the combination of the acting TRs in response to a control signal. CONSTITUTION:When an instruction I is given to an output port circuit 6 from an instruction program array (IPLA), P TRs 22, 24 or a NOR gate 20 are turned off, an NTR 23 is turned on and an L signal is sent to an inverter 25. Then an NTR 28 is turned on and an L level is given to an external device from a pad 30. On the other hand, NTRs 28, 29 are both turned on by an instruction II and an external device is driven by a large driving capability. Thus, the driving capability is easily changed and the semiconductor integrated circuit device whose performance is enhanced along with the application request with a wide range by the user is obtained.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Field of Application Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems Action Embodiment An Embodiment of the Present Invention (Figure 1.2) Invention [Summary] The purpose of this invention is to provide a semiconductor integrated circuit device that can easily change the driving ability of an output circuit to improve performance by using a predetermined instruction code, and to drive an external circuit. The output circuit includes an output circuit and a control circuit that outputs a control signal corresponding to the driving capacity of an external circuit, the final stage of which is a combination of transistors that operate in accordance with the control signal. The drive capacity of the external circuit is changed by changing the drive capacity of the external circuit.

[Industrial application field]

The present invention relates to a semiconductor integrated circuit device, and more particularly to a semiconductor integrated circuit device whose driving capability can be controlled.

TTL is the mainstream in logic circuits in the IC field,
Although the internal logic is composed of MO3 elements, most of them are designed with input from a TTL IC or drive of a TTL IC in mind.

In this case, the drive ability is particularly related to noise, and the IC
This is one of the important matters that must be considered from the design stage.

[Conventional technology]

In conventional semiconductor integrated circuit devices, such as one-chip microcomputers, the size of transistors in the output circuit is uniformly determined at the circuit design stage according to usage conditions, and the driving capability is constant. - In general, the drive capacity varies depending on the size of the transistor, and the larger the transistor, the greater the drive capacity.On the other hand, increasing the drive capacity also has the disadvantage of increasing noise, so to suppress noise, reduce the drive capacity. There is a need to. In particular, an overshoot that occurs when the output signal falls from "H" to "L" causes a so-called glitch, which affects subsequent stages, resulting in undesirable noise. Therefore, in the conventional technology, the size of the transistor is determined to be a predetermined value at the design stage when the usage conditions are the same, taking both into consideration.

[Problem to be solved by the invention]

However, in such conventional microcomputers, the transistor capacity is determined at the design stage and cannot be changed, which limits the way users can use it and makes it difficult to meet wide-ranging usage requirements. For example, if the transistor driving ability could be changed even after manufacturing has been completed, the range of uses in relation to noise would be greatly expanded, leading to improved performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor integrated circuit device that can easily change the driving ability of an output circuit using a predetermined instruction code to improve performance.

Make the force variable.

Therefore, the driving capacity can be easily changed and the performance is improved.

[Means to solve the problem]

In order to achieve the above object, the semiconductor integrated circuit device according to the present invention aims to provide a semiconductor integrated circuit device that can easily change the driving ability of an output circuit using a predetermined instruction code to improve performance. and a control circuit that outputs a control signal corresponding to the driving capability of an external circuit, the final stage of which is comprised of a plurality of output transistors, the transistors operating according to the control signal. By changing the combination of the two, the driving ability of the external circuit can be changed.

[Effect]

In the present invention, when a predetermined instruction code is output from the control circuit, the output circuit changes the combination of operations of the plurality of transistors in the final stage to drive the external circuit. I will explain.

FIG. 1.2 is a diagram showing an embodiment of the semiconductor integrated circuit device according to the present invention, particularly an example applied to a one-chip microcomputer. First, the configuration will be explained. In FIG. 1, 1 is a one-chip microcomputer, and the microcomputer 1 includes a CPU 2, a ROM 3, and an R
AM4, IPL A (Ins-truction P
Logic Array) 5 and output port circuits 6 to 8.

CPU2 reads the instruction code written in ROM3.
Decode with PLA5 and perform the necessary arithmetic processing,
If necessary, instructions (I) and (II) are sent from the I PLA 5 to the output boat circuit (
Corresponding to the output circuit) Outputs to 6 to 8. RAM4 is CPU
It stores programs necessary for the processing in step 2 and temporarily stores data.

Output port circuits 6 to 8 receive commands (1) (
If), the circuit outputs a binary level signal corresponding to the calculation result to the outside, and its driving ability can be controlled in two stages. The CPU 2, ROM 3, RAM 4, and IPLA 5 collectively constitute a control circuit 11.

Here, the output port circuits 6 to 8 are all the same circuit, and one of them, the output port circuit 6, is shown in detail as follows.
It is expressed as shown in Figure 2. In FIG. 2, the output port circuit 6 includes PMO3) transistors (hereinafter referred to as PMO3) 21 and 22 that constitute the NOR gate 20 and NMO3) transistors (hereinafter referred to as PMO3) 21 and 22 and
3 transistor (hereinafter referred to as NMO3) 23, 24, PMO 326 and NMO that constitute the inverter 25
S27 and NMOS28.2 as output transistor
9 and an output pad 30. The NOR gate 20 outputs the NOR logic of instructions (1) and (n) to the inverter 25, and the inverter 25 outputs a signal obtained by inverting the NOR logic to NM.
Supplied to the gate of OS28. Further, the instruction (II) is supplied to the gate of NMOS29, and NMOS28
．． 29 is turned on/off according to the level of the gate supply signal and transmits logic to the output pad 30. In this case, N.M.O.
The NMOS 32B has a larger driving capacity than the NMOS 29. Instructions (I) and (II) are both high active, and when instruction (I) is transmitted to the output port circuit 6, only NMOS 28 is turned on, and when instruction (It) is transmitted, both NMOS 28 and 29 are turned on. Turn on.

In the above configuration, RO
The instruction code written in M3 is decoded by IPLA 5, necessary operations are performed, and instruction (1) or (II) is sent from IPLA 5 to output boat circuits 6 to 8 as appropriate. For convenience of explanation, taking the output boat circuit 6 as an example,
If the command (1) is now supplied from the IPLA 5 to the output port circuit 6, the NOR gate 20 outputs PMO321, P
MO322 and NMOS24 are turned off, NMoS23 is turned on, and a ``L'' signal is sent to the inverter 25, which is inverted and applied as an H'' signal to the gate of NMO32B. At this time, the gate of NMOS29 is “L”
It's on the level. Therefore, NMOS28 turns on and “L”
"The level logic is transferred from the output pad 30 to an external device (
(equivalent to an external circuit), and external devices are driven by the driving ability of the NMO 32B.

On the other hand, when the instruction (n) is supplied to the output port circuit 6, the NOR gate 20 outputs PMO322 and NMOS2.
4 is turned on, PMO 321 and NMOS 23 are turned off, and an L'' signal is transmitted to the inverter 25, but in the end,
NMO32B is turned on similarly to the above example. Also, NM
Since the command (n) becomes active and an H'' signal is supplied to the gate of the OS 29, the NMOS 29 is turned on.

As a result, both NMOS 28 and 29 are turned on, and the external device is driven with a large driving capability.

In this way, when the command (1) is issued, only the NMO32B is turned on and the driving capacity is small, and when the command (II) is issued, the NMO32B is turned on and the driving capacity is small.
32B and 29 are both turned on, increasing the driving capability.

Therefore, although the processing speed is slow for instruction (1),
On the other hand, with instruction (II), the speed is fast but the noise is large. Therefore, if you appropriately use the processing speed and noise tolerance depending on the external device, you can use a wide range of applications that meet the user's requirements. It is now possible to use it and improve performance.

Note that in the above embodiment, two types of commands are used to change the driving ability to two levels, but the invention is not limited to this; for example, the active ability can be changed to three or more levels by using three or more types of commands. .

In addition, the above embodiment is an example in which the output level is pulled down, and this takes into account the fact that glitches are likely to occur when pulling down, and is often applied in this way. However, the present invention It can also be applied in cases where Of course, it can also be applied to cases where both pull-down and pull-up are performed.

Furthermore, the present invention is applicable not only to microcomputers but also to other devices.

〔Effect of the invention〕

According to the present invention, the driving ability of the output circuit can be easily changed by a predetermined command, and performance can be improved in accordance with the wide range of usage requirements of users.

[Brief explanation of the drawing]

1.2 is a diagram showing an embodiment of a semiconductor integrated circuit device according to the present invention, FIG. 1 is a diagram showing its overall configuration, and FIG. 2 is a diagram showing an example of its output port circuit. 1...Microcomputer, 2...
CPU. 3...ROM. 4...RAM. 5... IPLA. 6-8...Output port circuit (output circuit), 11
...control circuit. ] , Microconvenience Store 5°1pLA2 :C
PU 6-8: Output port circuit (output circuit) 3: ROM 11: Control circuit 4 ° RAM

Claims (1)

[Claims] An output circuit includes an output circuit that drives an external circuit, and a control circuit that outputs a control signal corresponding to the driving capability of the external circuit, and the final stage of the output circuit includes a plurality of output transistors. , a semiconductor integrated circuit device characterized in that it is configured to change the combination of transistors that operate according to the control signal to change the driving ability of an external circuit.