Iii-9 input/output ports, Input ports (k ports), Structure of input port – Epson S1C33210 User Manual

Page 363

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

∗

for K60–K63

∗

Available only for K50–K52

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

Therefore, when these ports are used as high-level or low-level input ports, the high level must be AV

, and the low

level V

If there is a potential difference between AV

and V

, in particular, if the level from outside is V

, a current

may flow in the input buffer (when AV

> V

) or between V

and AV

(when AV

< V

). Therefore, if

these ports are not used, when the input level is fixed externally, it should be fixed at V

or AV