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_RST
Also, the _RST signal to the device can be monitored. This is an active low signal and should only be asserted
during power up. The _RST signal is driven by the PURX line.
The state of pins 19 & 18 (GPO1 and GP02 respectively) on the rising edge of the _RST pin determines what
interface is selected when the device powers up.
Bus Name
Bus Mode
I2C
2-Wire
SPI
CBus
3-Wire
It's possible that if GP01 and/or GPO2 are not at the correct state when the Si4713 device has power applied
then the wrong bus mode could be selected and the handset would be unable to communicate with the
device. For RM-235, the bus mode should be I2C.
_SEN
The _SEN pin is used to select one of two possible 7-bit I2C bus addresses. When _SEN is low, the I2C bus
address for the Si4713 device is 0010001 (0x11). When _SEN is high, the I2C bus address for the Si4713 is
1100011 (0x63).
If the _SEN signal is not correct (i.e. not selecting the correct I2C address), then this is also another possible
reason why control of the FMTx 2.x feature might not be possible. For RM-235 the I2C address used for FMTx
2.x will be 0x63.
I2C address
0010001 (0x11).
1100011 (0x63).
FMTx2.0 specific RF test points
TXO
Pin 4 is the TXO pin. This is the transmitter output pin and probe access can be obtained easily on one side
of the large inductor component. (L2600 – see figure 2). Using a high impedance probe and a spectrum
analyser it would be possible to examine the TXO pin and check that the transmitter is outputting a signal.
Specific clock test points
RCLK
Pin 9 is the RCLK (Reference Clock) input to the device. This is typically 32.768KHz and is driven from the sleep
clock from the base band. When measuring this clock frequency, it may be seen to vary by as much as +/-
120 ~ 200ppm. The device can only typically tolerate +/- 20ppm in order to maintain transmit frequency
accuracy. To overcome this, the software driver for the device calculates what the actual sleep clock (RCLK)
frequency is and periodically programs the device with this frequency.
Page 7 –8
Table 10 Bus mode selection truth table.
GPO1
High
SPI
High
Low (must
drive)
Table 11 I2C 7-bit bus address selection summary
_SEN
Low
High
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GPO2/IRQ
Low
Low (must drive)
Low
RM-235
FMTx 2.0 troubleshooting
Issue 1
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