STM32F4 Discovery : Why U4A and U4B in schematics when the MCU is marked as U4 on the PCB?

[skrowten_hermit]

I'm just learning to read and use schematics and I found that while physically the MCU (STM32F407VG on my STM32F4 Discovery board) is marked U4 as the part number on the PCB, the schematic (Section "STM32Fx" of "MB997-F407VGT6-D01_Schematic.pdf") shows 2 separate blocks U4A and U4B. I understand that U4A is the ports with the pins for I/O or peripheral interfacing. I have the following questions:

1. What exactly is U4B?
2. Why is U4 split this way?

It would be great if I get answers to the above questions. I have attached a screen grab of the same below.

[Peter BENSCH · Accepted solution]

1. As you have already mentioned, the U4A block contains the digital in-/outputs. U4B is the part of U4 that has to do with power supply, so no digital in-/outputs.
2. It has been splitted to make it clearer.

Regards

/Peter