RTX-24EM
User guide
The technical characteristics can change without notice. AUR°EL S.p.A doesn’t assume the responsibility to the damages caused by an improper use of the device.
AUR°EL S.p.A.
Via Foro dei Tigli, 4 - 47015 Modigliana (FC) – ITALY 12/11/2019 - Rev. B
Tel.: +390546941124 – Fax: +390546941660 Page 12
http://www.aurel.it
7.1
Power Down
This mode is enabled when ENABLE (Pin 10) or nRESET (Pin 4) is tied to GND. EM9209 internal regulators
and the voltage reference are disabled and the supply current is < 1uA.
7.2
Standby Mode
When ENABLE (Pin 10) or nRESET (Pin 4) is high the RTX-24EM wakes up in standby mode at about t
PD-STBY
seconds (see Table 6). The SPI register memory is then set to 0 and the SPI waits for the host programming.
In standby mode all internal circuits are disabled and can be accessed, including the crystal oscillator. The
host microcontroller can program the RTX-24EM for any operational mode.
7.3
RAM2 Init
The RTX-24EM can be configured using a 16 registers memory RAM2. RAM2 is resetted to 0 when ENABLE
(Pin 10) or nRESET (Pin 4) is set from GND to Vcc. In order to avoid 16 different SPI write cycles, a dedicated
subroutine located at
ROM_BOOT_Address = 0
will initialize most RAM2 addresses to their default values.
This procedure takes about t
RAM2_INIT
seconds (see Table 6).
7.4
Auto-cal
VCO center frequency
The RTX-24EM frequency synthesizer has an Auto-calibration mode that must be run periodically by the
host microcontroller. This keeps the channel frequency and FSK modulator operating within specification.
Analog components in this block are sensitive to temperature variation, therefore performance may
degrade or the link may fail if not run periodically. Typically, Auto-calibration should be run when changing
channels or if the operating temperature changes by more than 10 to 20 °C. This procedure takes about
t
VCO_CAL
seconds (see Table 6).
PTAT reference current
The internally generated PTAT current can be self calibrated using an internal PTAT generator.
This
procedure takes about t
PTAT_CAL
seconds (see Table 6).
7.5
Transmit
In Transmit mode, the RTX-24EM outputs a FSK-modulated packet, it returns to receive mode or standby
mode with the crystal oscillator enabled and sets the interrupt pin IRQ high. Depending on the choosen
subroutine the RTX-24EM can transmit the whole TXFIFO (till TXFIFO size = 0) or a predefined number of
bytes programmed in RAM2.
Transmit mode is activated from Receive mode or from Standby mode (with crystal oscillator enabled)
using the SPI command
Send_TXFIFO
.
7.6
Receive
The RTX-24EM in receive mode waits for a FSK-modulated packet. After receiving a suitable packet it sets
the IRQ pin high. Depending on the choosen subroutine, it can either read the size of the packet to be
received in the header or in RAM2.
