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III PERIPHERAL BLOCK: INPUT/OUTPUT PORTS
S1C33L03 FUNCTION PART EPSON B-III-9-1
A-1
B-III
I/O
III-9 INPUT/OUTPUT PORTS
The Peripheral Block has a total of 42 input/output ports. Although each pin is used for input/output from/to the
internal peripheral circuits, some pins can be used as general-purpose input/output ports unless they are used for
the peripheral circuits.
Input Ports (K Ports)
Structure of Input Port
The Peripheral Block contains 13 bits of input ports (K50 to K54, K60 to K67).
Figure 9.1 shows the structure of a typical input port.
Input interrupt
circuit
Kxx
KxxD
V
DDE
∗1
∗2
∗1 AV
DDE
for K50 and K60–K67
∗2 Available only for K50–K54
V
SS
Address
Internal data bus
Figure 9.1 Structure of Input Port
Each input-port pin is connected directly to the internal data bus via a three-state buffer. The state of the input
signal when read at an input port is directly taken into the internal circuit as data.
When K50 is used as an input port and K60 to K67 are used as general-purpose input ports, the power supply for
the port input buffers is AV
DDE.
Therefore, when these ports are used as high-level or low-level input ports, the high level must be AV
DDE, and the
low level V
SS.
If there is a potential difference between AV
DDE and VDDE, in particular, if the level from outside is VDDE, a
current may flow in the input buffer (when AV
DDE > VDDE) or between VDDE and AVDDE (when AVDDE < VDDE).
Therefore, if these ports are not used, when the input level is fixed externally, it should be fixed at V
SS or AVDDE.
The K50 port is provided with a pull-up resistance that pulls the port up to AV
DDE.