NXP Semiconductors K32 L2A Series, Reference Manual, Page: 514 / 1379

Figure 21-2. Auto Power Down Sequence
These operations can be done manually by software by writing to appropriate bits
(SCEN, SRST and VCC_EN) in the PCSR register or automatically by hardware under
the following conditions provided the auto power down feature is enabled in the PCSR
register.
• Setting the SPD bit in PSCR register by software
• Assertion of RTE bit in RX_STATUS register
• Assertion of SPDIF bit in PCSR register when configured to detect card removal
NOTE
The SPDES bit in PCSR register determines which edge
transition of the Smart Card Presence Detect pin is used for
Smart Card presence detection. Presence detection can be used
to determine if the card has been inserted or removed. The
occurrence of the edge specified by SPDES bit will cause the
following: SPDIF to be set; if the SPDIM mask is clear, an
interrupt to the CPU; and if SAPD in the PCSR register is set,
an auto power down sequence to begin. If Smart card insertion
is expected, SAPD can be set low to avoid the auto power down
sequence from falsely triggering. The bit SPDP can be used to
determine the current state of the Smart Card Presence Detect
pin.
NOTE
The auto power down operation requires a low frequency clock
(usually 32 kHz clock source) to be active on the device.
The auto power down sequence will clear the following register bits upon power down
sequence completion:
• SPD bit in PCSR register
• SCEN bit in PCSR register
Functional Description
K32 L2A Reference Manual, Rev. 2, 01/2020
514 NXP Semiconductors