Part # Application Note Television ST92195 ST92T195 ST92R195C 8-bit MCU for TV AN1868 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics


Part Details:

AN1868 APPLICATION NOTE ST92X195 C LANGUAGE CODE OPTIMIZED OSD SOFTWARE 1 INTRODUCTIONIn order to offer improved user interfaces (due to the continuous improvement of TV applica-tions), embedded OSD menus in TVs have become more and more complex (in number andappearance). Due to this complexity, the software s code size has continuously increased. This Application Note is dedicated to the management of these large OSD applications, usingST92x195 microcontrollers. These applications can use a large number of menus (and sub-menus) and also handle a complex navigation organization. Through the use of software instructions, this document will help you create the user interfacefor your TV chassis (language management and design considerations), using as little mem-ory as possible. The ST92195 microcontroller OSD is described in the following documents: ­ "ST92195 Datasheet", ­ "How to Manage the ST92195 OSD" application note (AN No. 9904002). 2 GENERAL CONSIDERATIONSEach menu is designed in the same way, i.e. by reusing several common patterns as manytimes as possible. To optimize ROM size, menus are designed with a limited number of shapes(the use of more than 2 or 3 shapes is prohibited). In order to design complex OSD applications, both parallel and serial modes are allowed. Thismeans that two TDSRAM memory blocks of display (user definable) are required to displaythe menu page: one for characters (block 0) and the other for attributes (block 1). Both of thesetwo blocks are user defined. The OSD screen contains a maximum of 23 rows of 40 characterseach. Header (row 0) and Status rows (rows 24 and 25) are not used. 3 OSD PICTURE DESIGNBefore a menu is displayed on the screen, it must be stored in ROM in one of the pre-definedtables. These tables describe, row by row, the characters and attributes defining this menu dis-play. Both the size and number of these types of tables must kept to a minimum. This is whyonly a small number of common patterns are created and then reused. An example of such a menu is described in Figure 1 Rev. 2 AN1868/0704 1/34 AN1868 - APPLICATION NOTE Figure 1. Example Menu MENU PictureSoundLanguageTeletext -Exit- This menu screen consists of 13 rows of 10 characters each. The cursor highlights the text ofthe current selection using a yellow background. The following three steps are required to display the OSD: ­ The appropriate characters (and/or serial attributes) are entered in the Display memory block (block 0). ­ The appropriate attributes (used to define the background colours or special effects (such as Flashing or Box mode) and to access special G3 characters, etc....) are entered in theAttribute memory block (block 1). ­ The menu messages are written in the Display memory block. These 3 steps are described in Figure 2 and in the sections that follow. 2/34 AN1868 - APPLICATION NOTE Figure 2. Menu Design Steps Foreground Color Background Color Propagation Menu PictureSound + Language + Teletext -- Exit -- Background Parallel Attibutes Messages Characters 3.1 BACKGROUND The background of an OSD menu consists of the characters allowed by the selected ST92195OSD font. The following characters are available for this font: ­ Normal characters (G0 or G2 characters), ­ Special characters (G3 characters) specifically designed for creating advanced menus. These special characters are accessible by adding a special parallel attribute in the Attributememory block (See "ATTRIBUTES" on page 5.). This is the background that will be used to display the selected text (messages).

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Application Note Television ST92195 ST92T195 ST92R195C 8-bit MCU for TV AN1868.pdf Datasheet