
S3C3410X RISC MICROPROCESSOR
SYSTEM MANAGER
4-15
EXTERNAL OUTPUT PORT REGISTER (EXTPORT)
You can use an external output latch device as an output port without any additional address logic for decoding
logic, because S3C3410X have the nWREXP pin. When you write any data to EXTPORT register, nWREXP pin
outputs a write strobe signal to interface with an external output latch device for latching the output data. That is,
the access signal to the external output latch device is controlled by writing any data to EXTPORT register. For
example, if you write 0xff to EXTPORT, memory controller outputs a write strobe signal in nWREXP pin and 0xff
in data bus. At this time, the access time is controlled by the extra device control register, EXTCON0 only. (Refer
to Figure 4-21)
When MDS mode is selected, this nWREXP pin is used as a write strobe signal for an external output latch,
which is emulated for port 7 output.
Register
Offset Address
R/W
Description
Reset Value
EXTPORT
0x203e
R/W
External Port Data register
0x0
EXTERNAL CHIP SELECTION DATA REGISTER (EXTDATX)
You can directly access to the external device as external memory without any additional address decoding logic
because S3C3410X have the external device control logic, nECS0 and nECS1 pins. These pins output the
external device selection signals. External device is accessed by the memory controller when the data is
read/write from/to EXTDAT0 or EXTDAT1. That is, if you read/write the data from/to EXTDAT0 or EXTDAT1, the
memory controller automatically outputs nECS0 or nECS1, the selected address and data. For example, if you
write 0xff to 0x206c in EXTDAT0, memory controller outputs nECS0 signal, 0x206c in address bus and 0xff in
data bus. At this time, the access time of EXTDAT0 and EXTDAT1 are controlled by the extra device control
register1, EXTCON1 only. (Refer to Figure 4-21)
When P2.7 or P3.7 is used as a normal input/output mode, nECS0 or nECS1 can not support extra chip
selection.
Register
Offset Address
R/W
Description
Reset Value
EXTDAT0
0x202c
R/W
Extra chip selection data register 0
–
0x206c
0x20ac
0x20ec
0x212c
:
0x2fec
EXTDAT1
0x202e
R/W
Extra chip selection data register 1
–
0x206e
0x20ae
0x20ee
0x212e
:
0x2fee