Canon EOS 20D Service Manual page 100

Technical Information
(2) Camera control circuit board
This board has six layers which include the following: The main
microcomputer which is an IC for camera operation control such as sensor
and mechanical control, the display microcomputer which is an IC for the
LCD panel and viewfinder display drive control and control of various
switches, an EEPROM which is memory for storing adjustment data (AE, AF,
etc.).
(3) External interface connection circuit board
To make the camera smaller, this board has been separated from the digital
control circuit board. It is located in the dead space between the camera body
and digital control circuit board.
The board is equipped with a USB port (MINI B) and video OUT terminal. It
provides USB 2.0 Hi-speed. Although this faster communication speed is
more prone to be affected by noise, the noise problem has been given
adequate consideration in the board's configuration.
(4) Flash circuit board
The electronic X circuit and camera orientation detection circuit have been
added to the flash circuit board. Also, the orientation detection circuit in
previous EOS cameras had two direction detection switches to detect the two
directions. In the EOS 20D, the orientation detection circuit has a 4-way
direction detection switch that can detect the horizontal and vertical
directions. By having only one switch, less space is necessary.
External interface connection
Flash circuit board
Digital control circuit board
circuit board
Fig. 033 Major circuit boards
Power supply circuit board
Camera control circuit board
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