2 IR LEDs for strong signal.
CPU - Unknown IC-on-board - Running at 4MHz. Connected to the Flash memory
Spansion S29AL016D70TF02 - 16M-bit FLASH Memory - for storing the firmware and Icons, etc.
The FLASH Memory uses the Common Flash Interface (CFI).
Slave CPU - Unknown IC-on-board - Connected to the EEPROM
24C16 - 16k-bit EEPROM - for storing all user info like codes and text, etc. This means the learned codes and setup are stored for at least 50 years without a battery.
There is a unpopulated resistor R6. Leave it alone. Unless you want to kill the remote.
Jumper J3 is a mini-B USB jack. It is not installed on newer remotes. But it looks like all hardware is there if you soldered one in. Seeing how it has been removed on remotes currently being sold, then that means there is little hope of us having the very usefull feature of updating the firmware.
The IR codes seem to be the same as the newest UR74A. It probably uses the same IC-on-board. The UR74A has the same 24C16 for memory. The current Code sheet on the X10 site for the IconRemote is not at all correct for the newest IconRemote as of at least January 2008. It may be correct for the first run.
X10 IR code for use with the IR543 is 0998.
It still has the RF code of 0999. Just not the RF transmitter. Adding the 3-pin RF daughter board makes it a full functioning X10 RF remote.