
S1C62740 TECHNICAL HARDWARE
EPSON
I-27
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Input Ports)
Interrupt function
All five bits of the input ports (K00–K03, K10) provide the interrupt
function. The conditions for issuing an interrupt can be set by the
software. Further, whether to mask the interrupt function can be
selected individually for all five bits by the software.
(1) K00–K03 interrupt
Figure 4.4.2 shows the configuration of K00–K03 interrupt circuit.
The interrupt selection register (SIK) and input comparison register
(DFK) are individually set for the input ports K00–K03 and can
specify the terminal for generating interrupt and interrupt timing.
The interrupt selection register (SIK00–SIK03) select what input of
K00–K03 to use for the interrupt. Writing "1" into an interrupt
selection register incorporates that input port into the interrupt
generation conditions. The changing the input port where the
interrupt selection register has been set to "0" does not affect the
generation of the interrupt.
The input interrupt timing can select that the interrupt be gener-
ated at the rising edge of the input or that it be generated at the
falling edge according to the set value of the input comparison
register (DFK00–DFK03).
By setting these two conditions, the interrupt for K00–K03 is
generated when an input port in which an interrupt has been
enabled by the input selection register and the content of the input
comparison register have been changed from matching to no
matching.
When the interrupt is generated, the interrupt factor flag (IK0) is
set to "1".
The interrupt mask register (EIK0) enables the interrupt mask to
be selected for K00–K03. However, the interrupt factor flag is set to
"1" when the interrupt condition is established regardless of the
interrupt mask register setting.
Figure 4.4.3 shows an example of an interrupt for K00–K03.
Fig. 4.4.2
Input interrupt circuit
configuration (K00–K03)
Data
bus
Input comparison
register (DFK00)
K00
Interrupt
request
Input selection
register (SIK00)
Address
Interrupt factor
flag (IK0)
K01
K02
K03
Interrupt mask
register (EIK0)
Address