ST25R3912 datasheet(47/130 Pages) STMICROELECTRONICS

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DS11794 Rev 9

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ST25R3912

Functional overview

Clear RSSI

The receiver automatically clears the RSSI bits in the RSSI display register and starts to

measure the RSSI of the received signal when the signal rx_on is asserted. Since the RSSI

bits store peak value (peak-hold type) the variations of the receiver input signal will not be

followed (this may happen in case of long messages or test procedures). The direct

command Clear RSSI clears the RSSI bits in the RSSI display register, and the RSSI

measurement is restarted (in case, of course, rx_on is still high).

This command is accepted in case en (bit 7 of the Operation control register) is set and Xtal

oscillator frequency is stable.

Direct command chaining is possible.

IRQ due to termination of direct command is not produced.

Transparent mode

Enters in the Transparent mode. The Transparent mode is entered on the rising edge of

signal /SS and is maintained as long as this signal is kept high.

This command is accepted when en (bit 7 of the Operation control register) is set and Xtal

oscillator frequency is stable.

Measure power supply

This command performs the power supply measurement. Configuration bits mpsv1 and

mpsv0 of the Regulator voltage control register define which power supply is measured

(VDD,VSP_A, VSP_D and VSP_RF can be measured). Result of measurement is stored in

the A/D converter output register.

During the measurement the selected supply input is connected to a 1/3 resistive divider,

whose output is multiplexed to A/D converter in absolute mode. Due to division by 3, one

LSB represents 23.438 mV.

Duration time: 25 μs max.

This command is accepted in case en (bit 7 of the Operation control register) is set and Xtal

oscillator frequency is stable.

Direct command chaining is not possible.

IRQ due to termination of direct command is produced after command execution is

terminated.

1.2.13

Start timers

See Section 1.2.6: Timers on page 23.

1.2.14

Test access

A direct command Test access is used to enable RW access of test registers and entry in

different test modes. Pins TO1 and TO2 are used as test pins.

Test mode entry and access to test registers

Test registers are not part of normal SPI register address space. After sending a direct

command Test access, test registers can be accessed using normal Read/Write register SPI

command. Access to test registers is possible in a chained command sequence where first

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