
S1C88409 TECHNICAL MANUAL
EPSON
139
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Serial Interface)
5.14.8 IR (Infrared-ray) interface
PPM
modulator
SOUT
(P15)
LED
TXD
LED A
LED C
RXD
CX1
Vcc
CX2
GND
VP1N
Photodiode
SIN
(P14)
VDD
VSS
Serial I/F
PPM
modulator
S1C88409
IR communication module
(Reference: HP HSDL-1000)
Fig. 5.14.8.1 Configuration example of IR interface
The serial interface has a built-in PPM modulator.
Thus a circuit for infrared-ray communication
based on IrDA (Infrared Data Association) stan-
dard can be configured by adding a simple
external circuit.
Setting of IR interface
The PPM modulator is only available when the
P14–P17 terminals are selected and the asynchro-
nous mode is set.
When using the IR interface, change the function
of the serial interface using the IRST register. (See
Table 5.14.8.1.)
At initial reset, the serial interface is set as general
interface.
When IR interface function is set, the serial
interface can reverse the logic polarity of the
input/output signal according to the infrared-ray
communication module to be connected to the
outside. It is negative logic usually. Reverse the
logic when inputting and outputting positive logic
signal.
The logic of the SIN input and SOUT output can
be individually set by the IRIL register and the
IRTL register. (See Tables 5.14.8.2 and 5.14.8.3.)
At initial reset, both the IRIL register and IRTL
register are set to "0" (logic not reversed).
Table 5.14.8.1 Setting of IR interface
IRST1
1
0
IRST0
1
0
1
0
Setting
Reserved (do not set)
IR interface is used
Reserved (do not set)
IR interface is not used (normal interface is set)
Table 5.14.8.2 Input logic of IR interface
IRIL
1
0
Setting
SIN input logic is reversed (HIGH active)
SIN input logic is not reversed (LOW active)
Table 5.14.8.3 Output logic of IR interface
IRTL
1
0
Setting
SOUT output logic is reversed (HIGH active)
SOUT output logic is not reversed (LOW active)