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5.4 Input Ports (K ports)
5.4.1 Configuration of input ports
The E0C88832/88862 is equipped with 9 input port
bits (K00–K07 and K10) which are usable as general
purpose input port terminals with interrupt
function.
K10 terminal doubles as the external clock (EVIN)
input terminal of the programmable timer (event
counter) with input port functions sharing the
input signal as is. (See "5.10 Programmable Timer")
Each input port is equipped with a pull-up resistor.
The mask option can be used to select either "With
resistor" or "Gate direct" for each input port.
Figure 5.4.1.1 shows the structure of the input port.
Kxx
Fig. 5.4.1.1 Structure of input port
Each input port terminal is directly connected via a
three-state buffer to the data bus. Furthermore, the
input signal state at the instant of input port
readout is read in that form as data.
E0C88832/88862 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Input Ports)
V
DD
Input
interrupt
circuit
Mask
option
KxxD
Address
V
SS
5.4.2 Mask option
Input port pull-up resistors
K00 ....
With resistor
K01 ....
With resistor
K02 ....
With resistor
K03 ....
With resistor
K04 ....
With resistor
K05 ....
With resistor
K06 ....
With resistor
K07 ....
With resistor
K10 ....
With resistor
Input ports K00–K07 and K10 are all equipped with
pull-up resistors. The mask option can be used to
select 'With resistor' or 'Gate direct' for each port
(bit).
The 'With resistor' option is rendered suitable for
purposes such as push switch or key matrix input.
When changing the input terminal from LOW level
to HIGH with the built-in pull-up resistor, a delay
in the waveform rise time will occur depending on
the time constant of the pull-up resistor and the
load capacitance of the terminal. It is necessary to
set an appropriate wait time for introduction of an
input port. In particular, special attention should be
paid to key scan for key matrix formation. Make
this wait time the amount of time or more calcu-
lated by the following expression.
Wait time = R
x (C
IN
R
: Pull up resistance Max. value
IN
C
: Terminal capacitance Max. value
IN
When 'Gate direct' is selected, the pull-up resistor is
detached and the port is rendered suitable for
purposes such as slide switch input and interfacing
with other LSIs.
In this case, take care that a floating state does not
occur in input.
For unused input ports, select the default setting of
"With resistor".
EPSON
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
+ load capacitance on the
IN
board) x 1.6 [sec]
33
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