III PERIPHERAL BLOCK: INPUT/OUTPUT PORTS

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.

Kxx

VDD *1

∗2

Input interrupt circuit

 

 

 

bus

 

KxxD

dataInternal

 

 

 

 

 

 

 

 

 

Address

 

 

VSS ∗ 1 AVDD for K60–K63

∗2 Available only for K50–K52

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 AVDD. Therefore, when these ports are used as high-level or low-level input ports, the high level must be AVDD,and the low level VSS.

If there is a potential difference between AVDD and VDD, in particular, if the level from outside is VDD, a current may flow in the input buffer (when AVDD > 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 VSS or AVDD .

S1C33210 FUNCTION PART

EPSON

B-III-9-1