Samsung S3C2440A - Manual (Page 269)

S3C2440A RISC MICROPROCESSOR I/O PORTS
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GPJDAT Bit Description
GPJ15:0] [12:0] When the port is configured as an input port, the corresponding bit is the pin state.
When the port is configured as an output port, the pin state is the same as the
corresponding bit.
When the port is configured as functional pin, the undefined value will be read.
GPJUP Bit Description
GPJ[12:0] [12:0] 0: the pull up function attached to to the corresponding port pin is enabled.
1: the pull up function is disabled.