Epson S1C88650 - Manual (Page 52)

44 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.
Input
interrupt
circuit
V DD
V SS
Data bus Kxx
KxxD
Address
Address
Pull-up
control
register
Mask option
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.
5.5.2 Mask option
Input port pull-up resistors
K00 .... ■ ■ With resistor ■ ■ Gate direct
K01 .... ■ ■ With resistor ■ ■ Gate direct
K02 .... ■ ■ With resistor ■ ■ Gate direct
K03 .... ■ ■ With resistor ■ ■ Gate direct
K04 .... ■ ■ With resistor ■ ■ Gate direct
K05 .... ■ ■ With resistor ■ ■ Gate direct
K06 .... ■ ■ With resistor ■ ■ Gate direct
K07 .... ■ ■ With resistor ■ ■ Gate direct
Input port Input I/F level
K00 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K01 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K02 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K03 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K04 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K05 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K06 .... ■ ■ CMOS level ■ ■ CMOS schmitt
K07 .... ■ ■ CMOS level ■ ■ CMOS schmitt
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).