GD32VF103 User Manual
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Figure 16-13. IrDA SIR ENDEC module
Normal
USART
Transmit
Encoder
Receive
Decoder
SIR MODULE
TX
RX
TX pin
RX pin
IREN
1
0
0
1
Infrared
LED
outside chip
inside chip
In IrDA mode, the polarity of the TX pin and RX pin is different. The TX pin is usually at low
state, while the RX pin is usually at high state. The IrDA pins keep stable to represent the
logic
‘
1
’
, while an infrared light pulse on the IrDA pins (a Return to Zero signal) represents the
logic
‘
0
’
. The pulse width should be 3/16 of a bit period. The IrDA could not detect any pulse
if the pulse width is less than 1 PSC clock. While it can detect a pulse by chance if the pulse
width is greater than 1 but smaller than 2 times of PSC clock.
Because the IrDA is a half-duplex protocol, the transmission and the reception should not be
carried out at the same time in the IrDA SIR ENDEC block.
Figure 16-14. IrDA data modulation
Normal
tx frame
Stop
Start
1
0
0
0
0
0
0
1
1
1
1
Stop
Start
1
0
1
1
1
1
0
0
0
0
0
TX pin
Normal rx
frame
RX pin
The SIR sub module can work in low power mode by setting the IRLP bit in USART_CTL2.
The transmit encoder is driven by a low speed clock, which is divided from the PCLK. The
division ratio is configured by the PSC[7:0] bits in USART_GP register. The pulse width on
the TX pin is 3 cycles of this low speed period. The receiver decoder works in the same
manner as the normal IrDA mode.