Fujitsu FR81S User Manual
CHAPTER 11: I/O PORTS
2. Features
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : I/O PORTS
FUJITSU SEMICONDUCTOR CONFIDENTIAL
4
2. Features
This section explains features of the I/O ports.
I/O multiplexing
If the I/O of multiple peripherals is assigned to one external pin, one of these peripherals is selected to be
used.
I/O relocation
If one pin for one peripheral can serve multiple external pins for I/O, one of these external pins is selected
to be used.
PORT function
External pins can be used for general-purpose I/O: if they are used for output, their values can be set and if
they are used for input, input values assigned to them can be read.
Figure 2-1 Diagram of I/O Multiplexing, I/O Relocation
Key code function
This function is for error writing protection. If writing is not executed to the key code register (KEYCDR)
according to the specified method, writing to the target register will become invalid. Also, word access for the
target register cannot be executed. The following are the key code target registers.
⋅
Data direction register
⋅
Port function register
⋅
Extended port function register
⋅
Port pull-up/down enable register
⋅
Analog input control register
⋅
DA control register
a peripheral
I/O multiplexing
peripheral A
peripheral B
peripheral C
I/O relocation
MB91520 Series
MN705-00010-1v0-E
399