JPH03192390A - Microcomputer for liquid crystal display - Google Patents

Abstract

PURPOSE:To change the display pattern of a liquid crystal display part without changing wiring between the liquid crystal display part and a chip by providing a switch circuit which makes selective connections between a segment bus and a holding circuit, and a strobe bus and the holding circuit. CONSTITUTION:A segment decoder 1 decodes four-bit segment data D00, D01, D02, and D03 showing the display contents to an LCD to select specific buses among seven segment buses seg1-seg7. A strobe decoder 2 decodes four-bit strobe data D10, D11, D12 and D13 which enable a display of respective digits of the LCD and selects one specific bus among four strobe buses stb1-stb4. An EPROM 6 performs ON/OFF control over transfer gates 4 and 5 with control data which are written previously according to the display data of the LCD. Consequently, L and C terminals of respective latch circuits 3-1-3-4 are connected selectively to one specific segment bus and strobe bus.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a microcomputer for liquid crystal display.

(b) Prior art In general, a liquid crystal display microcomputer that drives an LCD (liquid crystal display section) uses a segment decoder that selects a predetermined segment bus by decoding segment data that indicates the content to be displayed on the LCD. A strobe decoder that selects a predetermined strobe bus by decoding strobe data that enables display on the LCD, and a plurality of latch circuits that latch data for displaying a predetermined display at a predetermined position on the LCD at a predetermined timing. In addition, between the segment decoder and strobe decoder and the plurality of latch circuits, P is connected so that one predetermined segment bus and one predetermined strobe bus are connected to the input of one predetermined latch circuit. L A (p
It consists of a programmable logic array). Here, the PLA was created by determining connection points based on data determined using several masks (metal, contact, etc.).

(c) Problems to be solved by the invention However, in the above-mentioned conventional technology, the previous = own PLA
Since the PLA is created using a mask, the PLA cannot be built into an evaluation chip for program development, and the PLA must be provided outside the evaluation chip. Additionally, if you want to change the LCD display pattern, you must change the wiring between the LCD and the chip or create a new mask, which can lead to wiring errors and ignore mask change costs. First, there is a problem in that it is difficult to respond to changes in the display pattern of the LCD.

(d) Means for Solving the Problems The present invention was made to solve the above-mentioned problems, and it is possible to control a predetermined segment bus by decoding segment data indicating the display contents on the liquid crystal display section. A segment decoder to select, a strobe decoder to select a predetermined strobe bus by decoding strobe data that can be displayed on the liquid crystal display section, and a strobe decoder to select a predetermined strobe bus in synchronization with the transfer signal of one predetermined strobe bus. , a liquid crystal display microcomputer comprising a plurality of holding circuits that hold transfer signals of one predetermined segment bus, and a liquid crystal drive circuit that drives the liquid crystal display section based on the holding output of the holding circuit. , a plurality of switch circuits that selectively connect between the segment bus and the plurality of holding circuits and between the strobe bus and the plurality of holding circuits, and a plurality of switch circuits that selectively connect between the segment bus and the plurality of holding circuits, and a plurality of switch circuits that selectively connect the segment bus and the plurality of holding circuits, and , and a memory storing control data for connecting or disconnecting the plurality of switch circuits.

(E) Function According to the present invention, a plurality of switch circuits that selectively connect between a segment bus and a plurality of holding circuits and between a strobe bus and a plurality of holding circuits are arranged in a display pattern of a liquid crystal display section. Depending on the readout output of the memory, it can be placed in a connected or disconnected state.

(f) Example The details of the present invention will be specifically explained with reference to the drawings.

The drawing is a circuit diagram showing one embodiment of the present invention.

In the drawings, it is assumed that the driven LCD (not shown) has, for example, a four-digit 8 main display, and each digit 8 main display is formed by seven segments. The segment decoder (1) generates 4-bit segment data D0°, Dlml Dlml D, indicating the content to be displayed on the LCD.
Decode llll and decode 7 segment buses segl~
Select a predetermined bus in seg7. A strobe decoder (2) enables display on each digit of the LCD.
Bit strobe data D. ? DIle Dlm
l Decode Dll, 4 strobe buses 5tb
One predetermined bus from l-stb4 is selected. The latch circuits (3-1) to (3-4) are for displaying a predetermined display at a predetermined position on the LCD at a predetermined timing.

The transfer gate (4) has an input/output path that connects all the segment buses segl to seg7 and all the latch circuits (
3-1) to (3-4) are connected to the matrix intersection positions with the terminals 3-1) to 3-4. The transfer gate (5) has an input/output path connected to all the strobe knobs (5tbl to 5).
tb4 and C of all the latch circuits (3-1) to (3-4)
Connected to the matrix intersection with the (clock) terminal. Then, segment buses Segl to seg7, strobe buses 5tbl to 5tb4, and transfer game
) (4) A PLA is configured by (5). EP
The ROM (6) has the output of each element connected to the transfer game.
) The transfer gates (4) and (5) are connected to the control inputs of (4) and (5), and are controlled to turn on and off according to control data written in advance based on the display pattern of the LCD. This allows each latch circuit (
The L terminals and C terminals of 3-1) to (3-4) are selectively connected to one predetermined segment bus and strobe bus, respectively. For example, the control data in the EFROM (6) turns on the transfer gate (4) that connects the segment bus seg3 and the terminal of the latch circuit (3-1), and also turns on the strobe bus 5tbl and the latch circuit (3-1). ) is turned on, the transfer signals of the segment bus seg3 and strobe bus 5tbl are transferred to the latch circuit (3).
-1) When applied to the input terminal and the C terminal, the L terminal input is latched in synchronization with the timing of the C terminal input, and the L terminal input is latched in synchronization with the timing of the C terminal input.
It is output from the Q (output) terminal as a signal for displaying on the CD. The duty control circuit (7) is connected to the C terminals of the latch circuits (3-1) to (3-4), and controls the duty (1/1/2) for displaying on the LCD based on the duty control signal S. 1 (static) ~ 1/4
). The drive circuit (8) is connected to the output of the duty control circuit (7) and switches the bias for the LCD display based on the bias control signal S. Then, the LCD is driven by the output of the drive circuit (8), and a predetermined display is displayed on the LCD.

Here, the C terminal outputs of the latch circuits (3-1) to (3-4) each correspond to a predetermined 1 of the 4-digit figure 8 surface water on the LCD.
If it corresponds to a segment, the remaining 2 of the 4-digit figure 8 surface water, although not shown, are similar to the configuration in the drawing.
It is assumed that a latch circuit, a transfer gate, and an EFROM corresponding to four segments are provided.

From the above, between the segment buses segl-seg7 and the latch circuit terminals and the strobe buses 5tbl to 5t.
A transfer gate is connected between b4 and the C terminal of the latch circuit.
) (4) Since the connection is made selective according to (5), even if it is an evaluation chip for program evaluation, a PLA can be built in, and even if the LCD display pattern is changed, the LCD This makes it possible to respond quickly without changing the wiring between the device and the chip. Furthermore, when creating a PLA for a liquid crystal display microcomputer using a mask, the mask can be created reliably and easily since it can be created based on the write data of the E F ROM (6) of this embodiment.

Note that the E F ROM (6) of this embodiment may be a RAM, and in this case, the data stored in the RAM can be rewritten and controlled by a program.

(G) Effects of the Invention According to the present invention, since the segment bus and the holding circuit and the strobe bus and the holding circuit are selectively connected by the switch circuit, the display pattern of the liquid crystal display section Even if the PLA is changed, it can be handled without changing the wiring between the liquid crystal display section and the chip and without creating a new mask. can also be built into evaluation chips, etc., which provides advantages such as simplifying development tools.

[Brief explanation of drawings]

The drawing is a circuit diagram showing a microcomputer for liquid crystal display according to the present invention. (1)... Segment decoder, (2)... Strobe decoder, (3-1) to (3-4)... Latch circuit, (4) (5)... Transfer gate, (6)・
...EFROM, (8)...drive circuit.

Claims (3)

[Claims] (1) A segment decoder that selects a predetermined segment bus by decoding segment data indicating the content to be displayed on the liquid crystal display, and a strobe data that enables display on the liquid crystal display. a strobe decoder that selects a predetermined strobe bus; a plurality of holding circuits that hold a transfer signal of one predetermined segment bus in synchronization with a transfer signal of one predetermined strobe bus; and a holding circuit that holds the transfer signal of one predetermined segment bus. A liquid crystal display microcomputer comprising: a liquid crystal drive circuit that drives the liquid crystal display section based on an output; a plurality of switch circuits for selectively connecting the plurality of switch circuits; and a memory storing control data for connecting or disconnecting the plurality of switch circuits according to the display pattern of the liquid crystal display section. A liquid crystal display microcomputer characterized by comprising: (2) The microcomputer for liquid crystal display according to claim (1), wherein the switch circuit is a transfer gate. (3) The liquid crystal display microcomputer according to claim (1), wherein the memory is a nonvolatile memory or a volatile memory in which data can be written.