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EPSON
S1C63358 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Input Ports)
IK0: K0 input interrupt factor flag (FFF4H•D0)
IK1: K1 input interrupt factor flag (FFF5H•D0)
IK2: K20 input interrupt factor flag (FFF5H•D1)
These flags indicate the occurrence of input interrupt.
When "1" is read: Interrupt has occurred
When "0" is read: Interrupt has not occurred
When "1" is written: Flag is reset
When "0" is written: Invalid
The interrupt factor flags IK0, IK1 and IK2 are associated with K00–K03, K10–K13 and K20, respectively.
From the status of these flags, the software can decide whether an input interrupt has occurred.
The interrupt factor flag is set to "1" when the interrupt condition is established regardless of the inter-
rupt mask register setting. However, the interrupt does not occur to the CPU when the interrupt is
masked.
These flags are reset to "0" by writing "1" to them.
After an interrupt occurs, the same interrupt will occur again if the interrupt enabled state (I flag = "1") is
set or the RETI instruction is executed unless the interrupt factor flag is reset. Therefore, be sure to reset
(write "1" to) the interrupt factor flag in the interrupt service routine before shifting to the interrupt
enabled state.
At initial reset, these flags are set to "0".
SENON: K20 port key sense ON/OFF control (FF2BH•D0)
Controls the key sense function.
When "1" is written: On
When "0" is written: Off
Reading: Valid
When using K20 as a general purpose input port, fix this register at "1" (On).
When K20 is used for the key sense function, set SENON on during the key sense stage. If any key is
pressed (see Figure 4.5.4.1), the K20 port generates an interrupt to the CPU. Then set SENON to off (K20
port key sense OFF), turn the outside N-P-N transistor on using an output port and start the A/D con-
verter. The A/D converter converts the input voltage that varies according to the pressed key into a
digital value. The software can discriminates which key was pressed from the conversion result. After
that, turn SENON off to reduce current consumption.
V
DD
R1
R
R2
R3
A/D IN
K20
Output
SENON
register
Generate
an interrupt
Key set
MCU
Fig. 4.5.4.1 Key position sensing circuit
