III PERIPHERAL BLOCK: INPUT/OUTPUT PORTS

A-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 13 bits of input ports (K50 to K54, K60 to K67).

Figure 9.1 shows the structure of a typical input port.

Kxx

VDDE ∗1

∗2

Input interrupt circuit

 

 

 

bus

 

KxxD

dataInternal

 

 

 

 

 

 

 

 

 

Address

 

 

VSS ∗1 AVDDE for K50 and K60–K67 ∗2 Available only for K50–K54

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 AVDDE.

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

If there is a potential difference between AVDDE and VDDE, in particular, if the level from outside is VDDE, a current may flow in the input buffer (when AVDDE > 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 VSS or AVDDE. The K50 port is provided with a pull-up resistance that pulls the port up to AVDDE.

B-III

I/O

S1C33L03 FUNCTION PART

EPSON

B-III-9-1