2010-06-30
Page 18 of 42
IT430_Tech_doc.doc
VDD supply ripple voltage: 54 mV(RMS) max @ f = 0… 3MHz
and 15 mV(RMS) max @ f > 3 MHz.
4.3 Host Port Configuration: RTS_N and CTS_N
User can select the host port configuration between UART, SPI (slave) and I
2
C (master/slave)
during power up boot. At system reset, the host port pins are disabled, so there will be no port
conflict occurring. Depending on the host port type, the software enables the correct port drivers,
sets up the port hardware, configures the pins according to the port type and begins operations.
The port selection is not intended to be changed dynamically but only set once at power up.
Default host port is SPI (selected by internal pull up/down resistors that are present during power
up) and other host port configurations requires connection of external pull down (to 0V) or pull up
(to 1.8V) resistor at CTS_N and RTS_N pins, see table below.
Table 4
Host port boot strap
Host port
RTS_N
CTS_N
UART
-
Pull up 10 kohm
SPI (default)
-
-
I
2
C
Pull down 10 kohm
-
4.3.1 Host Port UART
UART is normally used for GPS data reports and receiver control. Serial data rates are selectable
from 1200 baud to 1.8432 Mbaud. Default baud rate is 4800 baud; default protocol is NMEA
(switchable to SiRF OSP binary). RX signal must be driven by host or pulled up externally.
4.3.2 Host Port SPI
The host interface SPI is a slave mode SPI:
■
Supports both SPI and Microwire formats
■
An interrupt is provided when the transmit FIFO and output serial register (SR) are both empty
■
The transmitter and receiver each have independent 1024B FIFO buffers
■
The transmitter and receiver have individual software-defined 2-byte idle patterns
■
SPI detects synchronization errors and is reset by software
■
Supports a maximum clock of 6.8MHz.
■
A timer is provided to generate an interrupt when:
Summary of Contents for IT430
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