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BT817Q-R Scheda tecnica(PDF) 20 Page - Bridgetek Pte Ltd. |
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BT817Q-R Scheda tecnica(HTML) 20 Page - Bridgetek Pte Ltd. |
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20 / 59 page ![]() Copyright © Bridgetek Pte Ltd 20 BT817/8 Advanced Embedded Video Engine Datasheet Version 1.1 Document No.: BRT_000302 Clearance No.: BRT#154 Block footprint sizes are not confined to powers-of-two, and are also not confined to be square. For 2D formats the block dimensions range from 4 to 12 texels. Using ASTC for the large ROM fonts can save considerable space. Encoding the four largest fonts in ASTC 8x8 formats gives no noticeable loss in quality and reduces the ROM size from 1 Mbytes to about 640 Kbytes. 4.3.3 ROM and RAM Fonts The BT817/8 has built in ROM character bitmaps as font metrics. The graphics engine can use these metrics when drawing text fonts. There are a total of 19 ROM fonts, numbered with font handle 16- 34. Fonts 31-34 are large ROM fonts encoded in ASTC 8x8 format. The user can define and load customized font metrics into RAM_G or external flash, making it possible to support a full range of Unicode characters with UTF-8 coding points. Each ROM font metric block has a 148 byte font table which defines the parameters of the font and the pointer of font image. The font table format is shown in Table 4-7. Address Offset Size(byte) Parameter Description 0 128 width of each font character, in pixels 128 4 font bitmap format, for example L1, L4 or L8 132 4 font line stride, in bytes 136 4 font width, in pixels 140 4 font height, in pixels 144 4 pointer to font image data in memory Table 4-7 Font Table Format The ROM fonts are stored in the memory space ROM_FONT. The ROM font table is also stored in the ROM. The starting address of the ROM font table for font index 16 is stored at ROM_FONT_ADDR, with other font tables following. The ROM font table and individual character width (in pixel) are listed in Table 4-8, Table 4-9 and Table 4-10. Font index 16, 18 and 20-31 are for basic ASCII characters (code 0-127), while font index 17 and 19 are for Extended ASCII characters (code 128- 255). The character width for font index 16 through 19 is fixed at 8 pixels for any of the ASCII characters. Font Index 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 Font format L 1 L 1 L 1 L 1 L 1 L 1 L 1 L 1 L 1 L 1 L 4 L 4 L 4 L 4 L 4 L 4 L 4 L 4 L 4 Line stride 1 1 1 1 2 2 2 3 3 4 7 8 9 1 1 1 4 1 8 2 3 3 0 3 9 Font width (max) 8 8 8 8 1 1 1 3 1 7 1 8 2 5 3 4 1 3 1 5 1 9 2 1 2 8 3 7 4 9 6 3 8 2 Font height 8 8 1 6 1 6 1 3 1 7 2 0 2 2 2 9 3 8 1 6 2 0 2 5 2 8 3 6 4 9 6 3 8 3 1 0 8 Table 4-8 ROM Font Table Font Index => 16/ 18 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 3 4 0 NULL 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 SOH 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 STX 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 ETX 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 EOT 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 ENQ 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 ACK 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 BEL 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 BS 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9 HT 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 |
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