FT810Q datasheet(22/60 Pages) FTDI

22 / 60 page

Document No.: FT_001165

FT81X

Embedded Video Engine

Datasheet Version 1.2

Clearance No.:

FTDI#440

4.2.4 Clock Frequency

By default the system clock is 60MHz when the input clock is 12MHz. The host is allowed to switch the

system clock to other frequencies (48MHz, 36MHz, 24MHz) by the host command “CLKSEL”. The clock

switching command shall be sent in SLEEP mode only.

When using the internal relaxation oscillator, its clock frequency is trimmed to be 12MHz at factory.

Software is allowed to change the frequency to a lower value by programming the register REG_TRIM.

Note that software shall not change the internal oscillator frequency to be higher than 12MHz.

4.3 Graphics Engine

4.3.1 Introduction

The graphics engine executes the display list once for every horizontal line. It executes the primitive

objects in the display list and constructs the display line buffer. The horizontal pixel content in the line

buffer is updated if the object is visible at the horizontal line.

Main features of the graphics engine are:



The primitive objects supported by the graphics processor are: lines, points, rectangles, bitmaps

(comprehensive set of formats), text display, plotting bar graph, edge strips, and line strips, etc.



Operations such as stencil test, alpha blending and masking are useful for creating a rich set of

effects such as shadows, transitions, reveals, fades and wipes.



Anti-aliasing of the primitive objects (except bitmaps) gives a smoothing effect to the viewer.



Bitmap transformations enable operations such as translate, scale and rotate.



Display pixels are plotted with 1/16th pixel precision.



Four levels of graphics states



Tag buffer detection

The graphics engine also supports customized built-in widgets and functionalities such as jpeg decode,

screen saver, calibration etc. The graphics engine interprets commands from the MPU host via a 4 Kbyte

FIFO in the FT81x memory at RAM_CMD. The MPU/MCU writes commands into the FIFO, and the graphics

engine reads and executes the commands. The MPU/MCU updates the register REG_CMD_WRITE to

indicate that there are new commands in the FIFO, and the graphics engine updates REG_CMD_READ

after commands have been executed.

Main features supported are:



Drawing of widgets such as buttons, clock, keys, gauges, text displays, progress bars, sliders,

toggle switches, dials, gradients, etc.



JPEG and motion-JPEG decode



Inflate functionality (zlib inflate is supported)



Timed interrupt (generate an interrupt to the host processor after a specified number of

milliseconds)



In-built animated functionalities such as displaying logo, calibration, spinner, screen saver and

sketch



Snapshot feature to capture the current graphics display

For

complete

list

graphics

engine

display

commands

and

widgets

refer

FT81x_Series_Programmer_Guide, Chapter 4.

4.3.2 ROM and RAM Fonts

The FT81x 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. The user

can define and load customized font metrics into RAM_G, which can be used by display command with

handle 0-15.

Each 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.

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