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III PERIPHERAL BLOCK: INPUT/OUTPUT PORTS
S1C33210 FUNCTION PART EPSON B-III-9-1
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 7 bits of input ports (K50 to K52, K60 to K63).
Figure 9.1 shows the structure of a typical input port.
Input interrupt
circuit
Kxx
KxxD
V
DD *1
∗2
∗1 AV
DD for K60–K63
∗2 Available only for K50–K52
VSS
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 K60 to K63 are used as general-purpose input ports, the power supply for the port input buffers is AV
DD.
Therefore, when these ports are used as high-level or low-level input ports, the high level must be AV
DD, and the low
level V
SS.
If there is a potential difference between AV
DD and VDD, in particular, if the level from outside is VDD, a current
may flow in the input buffer (when AV
DD > VDD) or between VDD and AVDD (when AVDD < VDD). Therefore, if
these ports are not used, when the input level is fixed externally, it should be fixed at V
SS or AVDD .