ST63156 datasheet(48/86 Pages) STMICROELECTRONICS

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KBYREG

Keyboard Input Register

(E5h, Read Only)

D7 D6 D5 D4 D3 D2 D1 D0

KBY0 Input Data Bit

KBY1 Input Data Bit

KBY2 Input Data Bit

Unused

Figure 56. Keyboard Input Register

D7-D3. These bits are not used.

KBY0-KBY2. These bits store the logic level pre-

sent at KBY0, KBY1 and KBY2 input pins. No reset

value. This input pins have CMOS levels with on-

chip pull-up resistor (100k

Ω typical).

D6-D3. These bits are not used.

BSW0-BSW2,BSW3. The writing into these bits

will cause the corresponding BSW open-drain out-

put line to switch to the programmed level. Unde-

fined after reset.

AFC A/D INPUT, KEYBOARD INPUTS

AND BANDSWITH OUTPUTS (Continued)

BSWREG

Bandswitch Output Register

(E9h, Write Only)

D7 D6 D5 D4 D3 D2 D1 D0

BSW0 Output Bit

BSW1 Output Bit

BSW2 Output Bit

Unused

BSW3 Output Bit

Figure 57. Bandswitch Output Register

INFRARED INPUT (IRIN)

The IRIN pin is directly connected to the NMI inter-

rupt and acts as external interrupt pin (refer to in-

terrupt description for additional information).

The enable/disable of this interrupt can be man-

aged with the write only IEN bit available in the

DA2 Data/Control Register (Address E2h, bit D7).

When this bit is set to one the interrupt is enabled

otherwise it is disabled.

The IRIN pin is RISING EDGE sensitive.

Application Note

When the IR interrupt is enabled, then a rising

edge on the IR pin will generate an interrupt; if the

IR interrupt is disabled, no IR interrupts can occur.

Care should be taken because if the IR pin is high

when the IR interrupt is enabled, an interrupt will

also be generated; the following method to elimi-

nate noise can also be used if the SW engineer

wishes to enable/disable the IR interrupt.

If a Low-cost infra-red receiver is used, the cus-

stomer may wish to test the IR signal by software

after an interrupt in order to verify that there is a

good pulse and not just noise. The IRIN pin cannot

be read, so in this case it should be connected in

parallel with another pin so the signal can be read.

Furthermore the IRIN pin is sensitive to a rising

edge interrupt; this means that the input to the pin

should be low in the presence of no infra-red sig-

nal, but since most infra-red receiver modules give

a high signal, the signal will need to be inverted

with a transistor.

ST63140,142,126,156

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