{"id":429,"date":"2016-08-08T12:51:31","date_gmt":"2016-08-08T19:51:31","guid":{"rendered":"https:\/\/www.crystalfontz.com\/blog\/?post_type=encyclopedia&#038;p=429"},"modified":"2016-08-08T12:51:31","modified_gmt":"2016-08-08T19:51:31","slug":"ddram","status":"publish","type":"encyclopedia","link":"https:\/\/www.crystalfontz.com\/blog\/glossary\/ddram\/","title":{"rendered":"DDRAM"},"content":{"rendered":"<p>DDRAM stands for Display Data <a href=\"https:\/\/www.crystalfontz.com\/blog\/glossary\/ram\/\" target=\"_self\" title=\"RAM stands for Random Access Memory. This is memory that may be written to some value, then later read. RAM is the normal memory in a computer system. RAM only holds data when the RAM is powered. If power is interrupted, the data stored in the RAM is lost.\" class=\"encyclopedia\">RAM<\/a>.<\/p>\n<p>The Display Data RAM holds the letters that get shown on the <a href=\"https:\/\/www.crystalfontz.com\/blog\/glossary\/lcd\/\" target=\"_self\" title=\"LCD stands for Liquid Crystal Display. An LCD is composed of two pieces of glass with a thin layer of liquid crystals between the glass layers. When a voltage is applied to the glass, the orientation of the crystals can be changed. This change in the crystal's orientation (called polarization) will make either a dark&hellip;\" class=\"encyclopedia\">LCD<\/a> of a character LCD module. For instance the letter &lsquo;A&rsquo; is stored in its ASCII equivalent 65<sub>DEC<\/sub> (0x41<sub>HEX<\/sub>) in the DDRAM.<\/p>\n<p>So a <a href=\"https:\/\/www.crystalfontz.com\/c\/character-lcd-displays\/character-x-lines\/20x2-character\/75\">20&times;2 character LCD<\/a> would have enough DDRAM to store 40 letters. The value in the DDRAM is used to find the correct bitmap in the <a href=\"https:\/\/www.crystalfontz.com\/blog\/glossary\/cgrom\/\" target=\"_self\" title=\"CGROM&nbsp;stands for Character Generator ROM. The CGROM stores the font that is displayed on a character LCD. When you tell a character LCD to display the letter 'A', it needs to know which dots to turn on so that we see an 'A'. This information is stored in the CGROM. By definition, (since it is&hellip;\" class=\"encyclopedia\">CGROM<\/a> (Character Generator <a href=\"https:\/\/www.crystalfontz.com\/blog\/glossary\/rom\/\" target=\"_self\" title=\"ROM stands for Read Only Memory. This is memory that is factory pre-programmed to hold some data. ROM is data that can be read, but cannot be written or changed.\" class=\"encyclopedia\">ROM<\/a>) or <a href=\"https:\/\/www.crystalfontz.com\/blog\/glossary\/cgram\/\" target=\"_self\" title=\"CGRAM stands for Character Generator RAM. Character LCDs include a fixed CGROM to define the bulk of the characters they display. However, since the CGROM cannot be changed the designers also included the CGRAM -- a small number of characters (typically 8) that can be redefined at run-time. These eight characters are usually mapped to&hellip;\" class=\"encyclopedia\">CGRAM<\/a> (Character Generator RAM), it is this small bitmap that gets displayed on the LCD.<\/p>\n<figure id=\"attachment_430\" aria-describedby=\"caption-attachment-430\" style=\"width: 700px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/www.crystalfontz.com\/product\/cfah2002aymijt-character-module-lcd-20x2\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-430 size-large\" src=\"https:\/\/www.crystalfontz.com\/blog\/wp-content\/uploads\/20x2Display-700x229.jpg\" alt=\"20x2 Character Display - crystalfontz.com\" width=\"700\" height=\"229\" srcset=\"https:\/\/www.crystalfontz.com\/blog\/wp-content\/uploads\/20x2Display-700x229.jpg 700w, https:\/\/www.crystalfontz.com\/blog\/wp-content\/uploads\/20x2Display-250x82.jpg 250w, https:\/\/www.crystalfontz.com\/blog\/wp-content\/uploads\/20x2Display-768x251.jpg 768w, https:\/\/www.crystalfontz.com\/blog\/wp-content\/uploads\/20x2Display-120x39.jpg 120w, https:\/\/www.crystalfontz.com\/blog\/wp-content\/uploads\/20x2Display.jpg 800w\" sizes=\"auto, (max-width: 700px) 100vw, 700px\"><\/a><figcaption id=\"caption-attachment-430\" class=\"wp-caption-text\">20&times;2 Parallel Character LCD Part Number: CFAH2002A-YMI-JT<\/figcaption><\/figure>\n<p>This term very likely has its beginning in the granddaddy of all LCD controllers, the venerable <a href=\"https:\/\/www.crystalfontz.com\/blog\/the-legendary-hd44780-controller\/\">Hitachi HD44780<\/a>.<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>DDRAM stands for Display Data RAM. The Display Data RAM holds the letters that get shown on the LCD of a character LCD module. For instance the letter &#8216;A&#8217; is stored in its ASCII equivalent 65DEC (0x41HEX) in the DDRAM. So a 20&#215;2 character LCD would have enough DDRAM to store 40 letters. The value [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}}},"class_list":["post-429","encyclopedia","type-encyclopedia","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>DDRAM - Crystalfontz LCD Glossary<\/title>\n<meta name=\"description\" content=\"DDRAM : DDRAM stands for Display Data RAM. 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