JPH03105486A - Logic lsi incorporating programmable input/output circuit - Google Patents

Abstract

PURPOSE:To select an input/output circuit format in a programmable state and to easily alter it on a user side by replacing a part where an aluminum master slice is applied with an EEPROM, etc., when the logic LSI is manufactured. CONSTITUTION:When only a memory transistor (TR) 5 of the EEPROM is ON, an input/output terminal 4 is a terminal with a pull-up resistance 1. Further, when only an EEPROM TR 6 is ON, the terminal 4 is an output terminal and when only an EEPROM TR 7 is ON, the terminal functions as an input terminal. Thus, the input/output terminal 4 of the LSI functions as combinations of the resistance 1, an output circuit 2, and an input circuit 3 according to combinations of ON/OFF states of the memory TRs 5, 6, and 7 of the EEPROM. Namely, there are three kinds of circuits dedicated to input and output and for both input and output plus whether or not there is the pull-up resistance, i.e. six kinds in total can be selected as the input and output circuits 2 and 3 having the EEPROM TRs 5, 6, and 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a logic LSI incorporating a programmable input/output circuit whose circuit format can be freely switched by the user. [Prior Art] A conventional device is only a chip enable terminal control circuit equipped with an electrically programmable memory element, as described in Japanese Patent Application Laid-Open No. 134997/1983, and is capable of inputting/outputting data, etc. The control circuit is also not electrically programmable. In addition, as stated in "Literature r Microcomputer Encyclopedia" (Asakura Shoten Publishing),
A PLA etc. incorporates an electrically programmable memory element into a programmable intersection array consisting of an AND array and an OR array, and each of the input circuit section, output circuit section, and pull-up resistor section seen in the present invention AND to connect the logic block and the external interface terminal of the LSI.
A programmable intersection array consisting of an array and an OR array is not used. [Problem to be solved by the invention] In conventional logic LSIs such as microcomputers, an aluminum master slice method is used. At the stage of LSI manufacturing, the input/output circuit format can be changed to input-only, input/output, or
It was manufactured with three types of output-only terminals. Therefore, once the user has decided on the input/output circuit format, in order to change the input/output circuit format, the LSI must be manufactured again, posing a problem that requires a large amount of cost and time. An object of the present invention is to provide an input/output circuit of a logic LSI with an EPROM or an EEPROM, to programmably select the input/output circuit format, and to enable the user to freely and easily change the format of the input/output circuit.

[Means for solving problems]

The above purpose is for logic LSIs such as microcomputers.
This is achieved by replacing the parts to which aluminum master slices are applied with rewritable read-only memory such as EPROM or EEPROM during the manufacturing stage. or. By providing a control register in the high-voltage decoder in the EEFROM data writing circuit, data can be written to the EEPROM easily and at high speed. [
Operation] EEPROM erases data when a high positive voltage is applied to the gate electrode, and is always in an ON state. When the gate electrode is connected to GND, data is written and the device operates so that it is always in the OFF state. The gate electrode of the EEPROM is applied with a positive high voltage by a high voltage decoder or connected to GND.
However, a programmable high voltage decoder control register controls the high voltage decoder to select memory transistors in the EEPROM to apply positive high voltage or to GND. By this, E E
The input/output circuit equipped with P ROM is for input only.
A total of 6 types of circuits can be programmably selected, including 3 types for both input and output, and 3 types for output only, and with or without a pull-up resistor, allowing the user to freely and easily change the circuits.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained in detail using the drawings. Figure 1 shows a system built into a logic LSI such as a microcomputer. FIG. 2 is an input/output circuit diagram equipped with an EEPROM. 4 is LSI input/output terminal, 5, 6, 7 are EEPROM
memory transistor, 1 is a pull-up resistor. 2
3 is an output circuit to the outside of a logic LSI such as a microcomputer, and 3 is an input circuit to the logic LSI such as a microcomputer. The source side of the memory transistor 5 of the EEPROM is connected to the pull-up resistor 1, and the drain side is connected to the human output terminal 4 of the LSI. EE
The source side of the PROM memory transistor 6 is connected to the output circuit 2, and the drain side is connected to the input/output terminal 4 of the LSI. The source side of the EEPROM memory transistor 7 is connected to the input/output terminal 4 of the LSI, and the drain side is connected to the input circuit 3. EEPROM memory transistor 5
, 6 and 7 are connected to a high voltage decoder 10 as shown in FIG. When only memory transistor 5 of EEPROM is ON. The input/output terminal 4 of the LSI is a terminal with a pull-up resistor 1. When only the memory transistor 6 of the EEPROM is ON, the input/output terminal 4 of the LSI functions as an output terminal. When only the memory transistor 7 of the EEPROM is ON, the input/output terminal 4 of the LSI functions as an input terminal. Like this E E P
ON state of memory transistors 5, 6.7 of ROM,
Due to the combination of the OFF state, the function of the input/output terminal 4 of the LSI becomes a combination of the pull-up resistor 1, the output circuit 2, and the input circuit 3. The fact that the memory transistors 5, 6, and 7 of the EEPROM can be programmably always turned on or off will be explained below.

Figure 2 shows EEFROM memory transistors 56, 7τ
Demonstrates the principle of always being in the ON or OFF state.
In FIG. 2, 8 indicates a memory transistor of the EEPROM, and the gate voltage is ■.

This shows that the current between the source and drain flows in the direction of the arrow. In FIG. 3, the vertical axis indicated by ID is the source of the memory transistor 8 of the EEPROM.
The horizontal axis, which shows the current between the drains and is shown in vG, is the EEPR.
The gate voltage of memory transistor 8 of OM is shown. (a
) is the characteristic (α) of the EEPROM memory transistor 8 after data erasure.If the threshold voltage is set sufficiently small, it can always be in the ON state, and the EEPROM memory In the characteristic (b) of transistor 8 after data writing, if the threshold voltage is set sufficiently large, O
Can be set to FF state. In other words, the threshold voltage is significantly different after erasing data and after writing data, and the gate voltage va is different from the characteristics after data erasing (a) and the characteristics after data writing (b).
By setting the threshold voltage of
It can be set to FF state.

FIG. 4 shows a data write circuit for an EEPROM memory transistor. Reference numeral 9 denotes a memory transistor of the EEPROM, 10 a high voltage decoder, which is connected to the gate of 11, and has the function of putting the memory transistor 9 of each EEPROM into a data writing state and a data erasing state. The high voltage decoder control register 11 is for each high voltage decoder 1.
0 (there are as many memory transistors 9 of the EEPROM) as the EEPRs connected to each high voltage decoder 10.
It has a function of controlling whether the memory transistor 9 of the OM is in a data write state or a data erase state,
It is a programmable register. By providing the high voltage decoder control register 11, the memory transistor 9 of the EEPROM can be programmably kept in the ON state or in the OFF state.
It can be set to FF state, and all EEPRs can be turned on at once.
The memory transistor 9 of OM can be controlled. According to the present invention, the input/output circuit section including the memory transistor of the EEPROM can be programmably configured to be input-only, input-only,
The effect is that a total of 6 types of circuits can be selected, including 3 types for both input and output, and 3 types for output only, and with or without a pull-up resistor. [Effects of the Invention] According to the present invention, the logic L of a microcomputer, etc.
SI input/output circuits can be divided into input-only circuits, input/output dual-purpose circuits,
A total of 6 types, including 3 types of output-only circuits and the presence or absence of a sol-up resistor, can be selected programmably, so users can freely and easily select the circuit according to their application.
This has the effect of allowing selection of input/output circuit formats for logic LSIs such as microcomputers.

[Brief explanation of drawings]

FIG. 1 is an input/output circuit diagram including an EEPROM built into a logic LSI such as a microcomputer according to an embodiment of the present invention, and FIG. 2 shows a gate voltage V in a memory transistor of the EEPROM. Figure 3 is a diagram showing the electrical characteristics of an EEPROM memory transistor after data writing and data erasing. FIG. 2 is a diagram showing a data write circuit of a memory transistor of FIG. 1... Pull-up resistor, 2... Output circuit, 3...
Input circuit, 4...1 LSI input/output terminal, 5, 6, 7,
8, 9...EEPROM memory transistor, 1o.
...High voltage decoder, 11...High voltage decoder control register. No. 2 Okaya 1 mouth No. 3 Kon No. 4 mouth

Claims (1)

[Claims] 1. In an input/output circuit of a logic LSI such as a microcomputer, the input/output circuit includes an input circuit, an output circuit, and a rewritable read-only memory, and the input circuit and the output It is possible to switch circuits using the rewritable read-only memory, and the specifications of the terminals of the logic LSI of the microcomputer etc. can be programmably divided into three types: input-only terminals, output-only terminals, and input/output terminals. A logic LSI with a built-in programmable input/output circuit, which is characterized by the ability to select from a total of six types, including the presence or absence of a pull-up resistor. 2. The rewritable read-only memory is EEPR.
A logic LSI incorporating a programmable input/output circuit according to claim 1, which is an OM or EPROM. 3. Claim 2, characterized in that the EEPROM data writing circuit is provided with a high voltage decoder control register, and data can be written into the EEPROM memory cells as many times as the number of bits in the high voltage decoder control register at one time.
A logic LSI with a built-in programmable input/output circuit as described in Section 1.