JP2005122381A - Input/output control device and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an input/output control device capable of easily varying the numbers of switches for connection and light-emitting elements. <P>SOLUTION: The input/output control device has a plurality of ports for connecting switches or light-emitting elements. The input/output control device includes an input buffer and an output buffer connected to the respective ports, and a selection register, a switch state register and a light-emitting element control register each of which has bits corresponding to the respective port. The state of the input buffer is recorded in the corresponding bits of the switch state register. The state of the output buffer is determined based on the corresponding bits of the light-emitting element control register. The output buffer is switched between a positive and a non-positive state by the selection register. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an input / output control device, and more particularly to an input / output control device for connecting a switch and a light emitting element.

  Many electronic devices such as printing apparatuses include an input / output device typified by an operation panel in which a switch for receiving an operation from a user and a light emitting element for indicating the state of the electronic device are arranged. In addition, since LED (Light Emitting Diode) is generally used as a light emitting element, it demonstrates below taking LED as an example.

  As for the switches and LEDs arranged on the operation panel or the like, the state of each switch is acquired and the lighting state of each LED is determined by controlling the input / output control device in charge of input / output control. An input / output control device in which an LED and a switch are connected is disclosed in Patent Document 1, for example. The input / output control device is generally composed of an ASIC (Application Specific Integrated Circuit).

  The numbers of switches and LEDs arranged on the operation panel are fixedly determined based on product specifications. For this reason, different input / output control devices are used for different products, and if the number of switches and LEDs arranged on the operation panel is changed due to specification changes, etc. even for the same product, the design of the input / output control device Change is required.

JP-A-6-77534

  However, it is advantageous in terms of cost if the basic circuit of the input / output control device can be used universally for products having different numbers of switches and LEDs. Even if the number of switches and LEDs in the same product is changed due to specification changes, etc., if the basic circuit of the input / output control device can be used without change, it is advantageous in terms of cost. It becomes. In this case, it is desirable that it can be realized with a configuration as simple as possible.

  An object of this invention is to provide the input / output control apparatus which can change easily the number of the switches and light emitting elements to connect.

In order to solve the above problems, according to the first aspect of the present invention,
An input / output control device having a plurality of ports for connecting switches or light emitting elements,
An input buffer and an output buffer connected to each port;
Each includes a selection register having a bit corresponding to each port, a switch status register, and a light emitting element control register,
The state of the input buffer is recorded in the corresponding bit of the switch status register;
The state of the output buffer is determined based on the corresponding bit of the light emitting element control register,
The output buffer may be switched between an active state and an inactive state by a selection register.

  Even if the light emitting element and the switch connected to the port are changed, it can be dealt with by setting the value of the selection register. Therefore, the number of switches and light emitting elements to be connected can be easily changed.

  Since the output buffer drives the light emitting element, it is preferable that the load current capacity is large, for example, 20 mA or more. Examples of the output buffer having a large load current capacity include an open drain type and an open collector type.

Moreover, in order to solve the said subject, according to the 2nd aspect of this invention,
Multiple ports,
An input buffer and an output buffer connected to each port;
Each includes a selection register having a bit corresponding to each port, a switch status register, and a light emitting element control register,
The state of the input buffer is recorded in the corresponding bit of the switch status register;
The state of the output buffer is determined based on the corresponding bit of the light emitting element control register,
The output buffer is switched to an active / inactive state by a selection register;
A light emitting element is connected to the port connected to the active output buffer,
An electronic device is provided in which a switch is connected to at least a part of a port connected to an inactive output buffer.

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

  FIG. 1 is a block diagram for explaining the configuration of a SW / LED control apparatus 10 to which the present invention is applied. The SW / LED control device 10 is used, for example, as a device that constitutes an electronic device, and specifically, can be used as an input / output control device that controls an operation panel or the like including a switch and an LED.

  In this figure, the SW / LED control device 10 includes a plurality of ports 60 (port (0) to port (N)), and each port 60 can be connected to an LED or a switch (SW). It is like that.

  In addition, the SW / LED control device 10 includes three registers: a SW / LED selection register 30, a SW state register 40, and an LED control register 50. Each register has a bit length of at least the number of ports 60, and each register has a bit corresponding to each port 60.

A buffer unit 20 is connected to each port 60. The buffer unit 20 is configured by connecting an input buffer 21 and a three-state output buffer 22 in parallel. The three-state output buffer 22 is enabled according to the value of the corresponding bit in the SW / LED selection register 30. Or it is controlled to an inactive state (disable).

  Here, as the three-state output buffer 22, a buffer having a large load current capacity, for example, 20 mA or more is used. Further, if an open drain type or an open collector type buffer is used as the output buffer 22, it can be used even if the power source of the ASIC including the buffer and the power source for driving the LED are different. For example, 3.3 V can be supplied to an ASIC incorporating an open drain type or open collector type buffer, and 5 V can be supplied to an LED power supply. Such a configuration is effective when it is desired to brighten the LED.

  When a switch is connected to the port 60, the signal state from the input buffer 21 based on the state of the switch is recorded in the corresponding bit of the SW state register 40. When an LED is connected to the port 60, the output state of the three-state output buffer 22 is controlled by the value of the corresponding bit in the LED control register 50 in the active state.

  FIG. 2A is a block diagram showing a case where the switch 70 is connected to the port 60. The on / off state of the switch 70 is taken out from the input buffer 21 and recorded in the SW state register 40. In this case, the three-state output buffer 22 is controlled to an inactive state (disable) based on the value of the SW / LED selection register 30, and the output side is in a high impedance state. The output signal from the LED control register 50 is not used. Even when the port 60 is not used, it is desirable that the output buffer 22 is inactive.

  FIG. 2B is a block diagram showing a case where the LED 80 is connected to the port 60. The three-state output buffer 22 is controlled to an active state (enable) based on the value of the SW / LED selection register 30, and the LED 80 is turned on / off based on the value of the LED control register 50. In this case, the signal of the input buffer 21 is not used.

  FIG. 3 shows the SW / LED control apparatus 10 having eight ports 60 (port (0) to port (7)), in which a switch is connected to the ports (0) to (2), and the ports (3) to (2) It is a figure which shows the case where LED is connected to (7).

  FIG. 4A shows an example of each register in this case. That is, each register has a width of 8 bits, and each bit corresponds to port (0) to port (7).

  The bit value of the SW / LED selection register 30 corresponding to the port 60 to which the switch is connected is set to 1, and the bit value of the SW / LED selection register 30 corresponding to the port 60 to which the LED is connected is set to 0. In this case, the setting of the SW / LED selection register 30 is “00000111” as shown in FIG.

  It can be determined according to the value of the SW / LED selection register 30 which bit is valid among the values of the respective bits of the SW status register 40 and the LED control register 50, that is, which bit is used.

  In this example, the SW status register 40 has a valid bit whose value of the SW / LED selection register 30 is “1”, and acquires the status of the switch connected to the corresponding port 60 from the value of the bit. Can do.

  In the LED control register 50, the bit whose value in the SW / LED selection register 30 is “0” is valid, and the LED connected to the corresponding port 60 is turned on / off by controlling the value of the bit. Can be changed. At this time, since the three-state output buffer 22 has a large load current capacity, the LED can be driven.

  As shown in FIG. 4B, the SW state register 40 and the LED control register 50 are combined into one SW / LED common register, and which role is based on the value of the SW / LED selection register 30. You may make it distinguish whether to carry. As a result, the number of registers can be reduced, and the switch 70 and the LED 80 can be controlled by a single register during operation. In the example of the figure, the SW / LED shared register is used as the SW status register until the 0th to 2nd bits, and the 3rd to 7th bits are used as the LED control register.

  Thus, according to the present invention, there is provided an input / output control device capable of easily changing the number of switches and light emitting elements to be connected.

The block diagram which shows the structure of SW / LED control apparatus. The figure which shows the example of a connection of a port and a switch, and a connection of a port and LED. The figure which shows the example of a connection of a some port. The figure which shows the state of each register.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... SW / LED control apparatus, 20 ... Buffer part, 21 ... Input buffer, 22 ... Output buffer, 30 ... SW / LED selection register, 40 ... SW status register, 50 ... LED control register, 60 ... Port, 70 ... Switch , 80 ... LED

Claims (7)

An input / output control device having a plurality of ports for connecting switches or light emitting elements,
An input buffer and an output buffer connected to each port;
Each includes a selection register having a bit corresponding to each port, a switch status register, and a light emitting element control register,
The state of the input buffer is recorded in the corresponding bit of the switch status register;
The state of the output buffer is determined based on the corresponding bit of the light emitting element control register,
The input / output control device, wherein the output buffer is switched to an active / inactive state by a selection register. The input / output control device according to claim 1,
An input / output control device characterized in that each bit of the switch status register and the light emitting element control register is determined to be used / not used based on a value of a corresponding bit of the selection register. An input / output control device having a plurality of ports for connecting switches or light emitting elements,
An input buffer and an output buffer connected to each port;
Each includes a selection register having a bit corresponding to each port and a shared register,
The state of the input buffer is recorded in the corresponding bit of the shared register when the input buffer is used.
The state of the output buffer is determined based on the corresponding bit of the shared register when the output buffer is used.
Use / non-use of the input buffer and the output buffer is selectively determined based on corresponding bits of the selection register,
The input / output control device, wherein the output buffer is switched to an active / inactive state by a selection register. In the input / output control device according to claim 1 or 3,
The output buffer has a load current capacity of 20 mA or more. In the input / output control device according to claim 1 or 3,
The output buffer is an open drain type or an open collector type input / output control device. Multiple ports,
An input buffer and an output buffer connected to each port;
Each includes a selection register having a bit corresponding to each port, a switch status register, and a light emitting element control register,
The state of the input buffer is recorded in the corresponding bit of the switch status register;
The state of the output buffer is determined based on the corresponding bit of the light emitting element control register,
The output buffer is switched to an active / inactive state by a selection register;
A light emitting element is connected to the port connected to the active output buffer,
An electronic device, wherein a switch is connected to at least a part of a port connected to an inactive output buffer. The electronic device according to claim 6,
Enable the bit of the light emitting element control register corresponding to the port connected to the output buffer in the active state,
An electronic device characterized by validating a bit of a switch status register corresponding to a port connected to an inactive output buffer.

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