DocID024597 Rev 5 1495/1830
RM0351 Single Wire Protocol Master Interface (SWPMI)
1517
Deactivate mode
In order to switch the SWP to the DEACTIVATED mode immediately, ignoring any possible
incoming RESUME by slave, the user must clear SWPACT bit in the SWPMI_CR register.
Note: In order to further reduce current consumption once SWPACT bit is cleared, configure the
SWPMI_IO port as output push pull low in GPIO controller (refer to Section 8: General-
purpose I/Os (GPIO)).
Figure 478. SWP bus states
44.3.4 SWPMI_IO (internal transceiver) bypass
A SWPMI_IO (transceiver), compliant with ETSI TS 102 613 technical specification, is
embedded in the microcontroller. Nevertheless, this is possible to bypass it by setting
SWP_TBYP bit in SWPMI_OR register. In this case, the SWPMI_IO is disabled and the
SWPMI_RX, SWPMI_TX and SWPMI_SUSPEND signals are available as alternate
functions on three GPIOs (refer to “Pinouts and pin description” in product datasheet). This
configuration is selected to connect an external transceiver.
44.3.5 SWPMI Bit rate
The bit rate must be set in the SWPMI_BRR register, according to the following formula:
F
SWP
= F
SWPCLK
/ ((BR[5:0]+1)x4)
Note: The maximum bitrate is 2 Mbit/s.
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