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Philips Semiconductors
2
4. I
C
In the above code examples for UART and SPI, interrupts have not been used but they
have been used for this example. I
is being used as a Master Transmitter and a Philips port expander PCF8574 is used as a
slave device. Waveforms are shown to help the user to understand the communication
better. VPB Divider value is at its reset settings and hence the peripheral clock is one
fourth of the system clock (10 MHz).
4.1 Calculation of Bit frequency
Since the maximum speed the PCF8574 could interface to the LPC2106 is100 KHz
Therefore
We select
Application note
Fig 3. Waveforms
Bit Frequency = pclk/ (I
100KHz= 2.5MHz/(I
2
2
I
CSCLH + I
CSCLL=25
2
I
CSCLH=13
&
2
I
CSCLL=12
Rev. 01 — 06 April 2005
Philips ARM LPC microcontroller family
0xC1
2
C has been classified as an IRQ interrupt. LPC2106
2
CSCLH + I
2
2
CSCLH + I
CSCLL)
AN10369
2
CSCLL)
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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