Input Ports (K Ports); Configuration Of Input Ports; Mask Option - Epson S1C88650 Technical Manual

5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Input Ports)

5.5 Input Ports (K ports)

5.5.1 Configuration of input ports

The S1C88650 is equipped with 8 input port bits
(K00–K07) all of which are usable as general purpose
input port terminals with interrupt function.
K04–K07 terminals doubles as the external clock
(EXCL0–EXCL3) input terminal of the
programmable timer (event counter) with input
port functions sharing the input signal as is. (See
"5.10 Programmable Timer")
Furthermore, it should be noted, however, that K03
terminal is shared with the bus authority release
_________
request signal (BREQ) input terminal. Function
assignment of this terminal can be selected in
software. When this terminal is selected for BREQ
signal, K03 cannot be used as an input port. (See
"5.2 System Controller and Bus Control")
In the explanation below, it is assumed that K03 is
set as an input port.
Figure 5.5.1.1 shows the structure of the input port.

Mask option

Kxx
Mask option
Fig. 5.5.1.1 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.
44
_________
V
DD
Pull-up
control
register
Address
KxxD
Address
Input
interrupt
V
SS
circuit
5.5.2 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
Input port Input I/F level
K00 .... CMOS level
K01 .... CMOS level
K02 .... CMOS level
K03 .... CMOS level
K04 .... CMOS level
K05 .... CMOS level
K06 .... CMOS level
K07 .... CMOS level
Input ports K00–K07 are all equipped with pull-up
resistors. The mask option can be used to select
'With resistor' or 'Gate direct' for each port (bit).
Also the interface level, either CMOS level or
CMOS Schmitt level, can be selected for each port
(in a bit units).
EPSON
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
Gate direct
CMOS schmitt
CMOS schmitt
CMOS schmitt
CMOS schmitt
CMOS schmitt
CMOS schmitt
CMOS schmitt
CMOS schmitt
S1C88650 TECHNICAL MANUAL