μC-LCD用户手册：嵌入式系统字符LCD控制指南

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"uc-LCD-Manual" 是针对嵌入式系统设计的一款微控制器（Microcontroller, 缩写为 µC）与字符液晶显示模块 (Character LCD) 的接口软件包。该手册主要针对 Hitachi HD44780 Dot Matrix LCD 控制器及驱动，它支持广泛的字符 LCD 模块，具有以下核心功能： 1. **LCD 控制**: - 支持控制最多包含 80 个字符的 LCD 模块。 - 实现对 ASCII 字符的显示，这是通过标准的字符集来操作的。 - 可以显示 ASCII 字符串，方便文本信息的显示。 2. **字符定义**: - 提供了 DispDefChar() 函数，允许用户自定义多达 8 个不同的符号或字符，这在需要特定符号显示或者定制界面时非常有用。 3. **接口函数**: - DispChar() 用于显示单个字符。 - DispClrLine() 清除一行显示。 - DispClrScr() 清除整个屏幕。 - DispHorBar() 和 DispVertBar() 分别用于显示水平和垂直线，可能用于指示器或分割屏幕。 - DispHorBarInit() 和 DispVertBarInit() 是这两个线条的初始化函数。 - DispInit() 用于初始化 LCD，确保正确的硬件配置。 - DispStr() 显示一整行字符串。 4. **硬件接口**: - DISP_BUS_WIDTH 设置 LCD 的数据总线宽度，影响数据传输速度。 - 提供了硬件接口函数如 DispDataWr() 用于写入数据，以及 DispDly_uS() 用于调整数据传输延迟，确保同步。 - DispInitPort() 初始化 LCD 接口端口，设置必要的寄存器。 - DispSel() 选择 LCD 的工作模式或地址，进行模块操作的选择。 5. **RTOS (Real-Time Operating System) 接口**: - 如果你的应用使用实时操作系统，手册会指导如何在 RTOS 环境下与 uc-LCD 模块协作，确保高效且同步的操作。 6. **文档结构**: - 用户手册包括目录、介绍部分、LCD 内部工作原理、接口功能详解、配置选项、RTOS 接口、参考文献以及联系信息。这款 uc-LCD 控制模块是嵌入式开发人员的宝贵工具，它简化了与字符 LCD 的交互，节省了宝贵的开发时间，并提供了丰富的功能以满足各种定制化需求。对于需要在项目中集成字符 LCD 的开发者来说，理解和掌握这份手册中的内容至关重要。

µC/LCD

User’s Manual

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useful when you have a low power application and want to turn off the backlight. It’s

actually possible to read the LCD module but µC/LCD doesn’t use that feature.

Four (or eight) of the lines are used for data transfer while the other four are used as

control lines for the LCD module.

The HD44780 takes a certain amount of time to process commands or data sent to it. The

Renesas datasheet provides you with the maximum amount of time required for each type

of data transfer. Because of this, the software can simply send a command or data and

wait at least the amount of time specified before sending the next command or data. Note

that the HD44780 itself allows the microprocessor to read a BUSY status. The BUSY

status can be read by the microprocessor to determine if the HD44780 is ready to accept

another command or more data. If you can, you should make use of the BUSY capability

of the HD44780 because this provides you with a true indication that the HD44780 is ready

to accept another command or more data. As a precaution, however, you should still

provide a timeout loop to prevent hanging up the microprocessor in case of a malfunction

with the interface electronics. Unless the LCD module is directly connected to the

microprocessor bus, implementing read capability with parallel I/O ports is a bit more

complicated since it requires that you change the direction of some of the I/O port lines.

The interface circuit is simplified by choosing to have the CPU wait between commands

and data. It turns out that this scheme also makes the software easier to write. Waiting is

done using µC/OS-II’s OSTimeDly() function or, the time delay of the function RTOS of

the RTOS you are using.

The LCD module appears as two read/write registers. The first register is called the data

is low). µC/LCD calls the instruction register the control register. Characters to display are

written to the data register. The control register allows the software to control the operating

mode of the module: clear the display, set the position of the cursor, turn the display ON or

OFF, etc.

µC/LCD

User’s Manual

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2.00 µC/LCD Internals

The source code for µC/LCD is found in the following directory:

\Micrium\Software\uC-LCD\Source. The source code is found in files LCD.C and

LCD.H. As a convention, all functions and variables related to the display module start with

Disp while all #define constants start with DISP_.

The code allows you to interface to just about any LCD module based on the Renesas

HD44780 LCD module controller. At first view, you might think that writing a software

module for an LCD module is a trivial task. This is not quite the case because the

HD44780 has its quirks. The HD44780 was originally designed for a 40 characters by 2

lines display (40x2) and thus has internal memory to hold 80 characters. The first 40

characters are stored at memory locations 0x80 through 0xA7 (128 to 167) while the next

40 characters are stored at memory locations 0xC0 through 0xE7 (192 to 231)! Tables 5.1

through 5.4 show the memory mapping for different LCD module configurations. The

addresses are shown in decimal and are actually based at 0x80. That is, address 00

actually corresponds to 0x80, address 64 is actually 0xC0 (i.e., 0x80 + 64), etc.

Table 2-1 shows the memory organization for 16-character displays. Notice how the 16

characters by 1 line module appears as a two-line display. This is done by the LCD module

manufacturers to reduce the cost of their product by fully using the drive capability of the

HD44780.

Table 2-2 shows the memory organization for 20-character displays. Again, the single-line

display appears as a two-line module.

Table 2-3 shows the memory organization for 24-character displays. As with the 16- and

20-character displays, the single-line display appears as a two-line module.

Table 2-4 shows the memory organization for 40-character displays. As with the other

module configurations, the single-line display appears as a two-line module. Note that

each line of a 40-character display is shown broken down into two separate lines; the

second line is offset from the first. This has been done to avoid reducing the character font

in order to fit within the width of the page.

µC/LCD will support any LCD module that is organized as shown in Table 2-1 through 2-4.

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μC-LCD用户手册：嵌入式系统字符LCD控制指南

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