S3C2440A has 130 multi-functional input/output port pins and there are eight ports as shown below:
— Port A(GPA): 25-output port
— Port B(GPB): 11-input/out port
— Port C(GPC): 16-input/output port
— Port D(GPD): 16-input/output port
— Port E(GPE): 16-input/output port
— Port F(GPF): 8-input/output port
— Port G(GPG): 16-input/output port
— Port H(GPH): 9-input/output port
— Port J(GPJ): 13-input/output port

Each port can be easily configured by software to meet various system configurations and design requirements. You have to define which function of each pin is used before starting the main program. If a pin is not used for multiplexed functions, the pin can be configured as I/O ports

从上面的信息可以看出，S3C2440芯片共有130个GPIO引脚，分为9组

关于GPIO的寄存器

PORT CONFIGURATION REGISTER (GPACON-GPJCON)
In S3C2440A, most of the pins are multiplexed pins. So, It is determined which function is selected for each pins.
The PnCON(port control register) determines which function is used for each pin.
If PE0 – PE7 is used for the wakeup signal in power down mode, these ports must be configured in interrupt mode.
PORT DATA REGISTER (GPADAT-GPJDAT)
If Ports are configured as output ports, data can be written to the corresponding bit of PnDAT. If Ports are configured
as input ports, the data can be read from the corresponding bit of PnDAT.
PORT PULL-UP REGISTER (GPBUP-GPJUP)
The port pull-up register controls the pull-up resister enable/disable of each port group. When the corresponding bit is
0, the pull-up resister of the pin is enabled. When 1, the pull-up resister is disabled.
If the port pull-up register is enabled then the pull-up resisters work without pin’s functional setting(input, output,
DATAn, EINTn and etc

关于如何设定寄存器，请参考芯片手册