Cypress FM4 Series - VBAT I;O Ports

CHAPTER 7-3: VBAT Domain(B)
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 319
2.6 VBAT I/O Ports
The FM4 Family has four I/O ports assigned to the VBAT Domain. These I/O ports (VBAT I/O ports) are
controlled by the port control circuit (VBAT port control circuit) of the VBAT Domain, and continued
operating even when the VCC power supply is turned off. The VBAT port control circuit is independent of
the port control circuit explained in Chapter I/O Port in FM4 Family Peripheral Manual. The addresses of
registers of the VBAT port control circuit are mapped to an area different the one to which the addresses
of registers of the port control circuit are mapped.
Overview of Function of VBAT I/O Ports
The VBAT I/O ports keep operating as long as the VBAT power supply is turned on, even when the VCC
power supply is turned off.
The VBAT I/O ports do not have the relocate function.
Configuration of VBAT I/O Ports
The registers of the VBAT port control circuit select the I/O direction, and the function of an I/O port
between GPIO port and peripheral function I/O pin.
For the configuration of the VBAT I/O ports, see Figure 2-1 in chapter I/O Port. (For registers having the
same function, substitute an actual register name for the one used in Figure 2-1.)
Table 2-8 shows a register list and explains the function of each register.
Table 2-8 Register List and Register Function
Register Name
Function
VBPFR[5:4]
This is a register setting whether to use a VBAT I/O port as a special pin (for oscillation) or as a digital I/O pin.
VBPFR[3:0]
This is a register setting whether to use a VBAT I/O port as a GPIO port or as a peripheral function I/O pin.
VBPCR[3:0]
With a VBAT I/O port used as a digital input pin or as a digital bidirectional pin, this is a register setting whether to
connect or disconnect the pull-up resistor of a VBAT I/O port.
VBDDR[3:0]
With a VBAT I/O port used as a GPIO port, this is a register setting whether to use that GPIO port as an input pin or
as an output pin.
Note: If a VBAT I/O port is used as a peripheral function I/O pin, the setting of this register becomes invalid.
VBDIR[3:0]
This is a register reading the level of a VBAT I/O port.
− If a VBAT I/O port is used as a digital input pin, this register reads the input level.
− If a VBAT I/O port is used as a digital output pin, this register reads the output level.
− If a VBAT I/O port is used as a special pin, this register always reads 0.
VBDOR[3:0]
With a VBAT I/O port used as a GPIO output pin, this is a register setting the output level.
− If a bit in VBDOR[3:0] is set to 0, a GPIO output pin outputs L level.
− If a bit in VBDOR[3:0] is set to 1, a GPIO output pin outputs H level.
Note: If a VBAT I/O port is used as a GPIO input pin or as a peripheral function I/O pin, the setting of this register
becomes invalid.
VBPZR[1:0]
This is a register controlling the open drain of a VBAT I/O port.
− If a VBAT I/O port outputs L level, I/O Port is set to L level output. (The pull-up resistor is disconnected regardless of the
setting of the PCR Register.)
− If a VBAT I/O port outputs H level, I/O Port is set to Hi-Z, and the open drain is controlled in pseudo manner. (The pull-up
resistor is disconnected regardless of the setting of the PCR Register.)
− If a VBAT I/O port is used as an input port, I/O Port is set to Hi-Z, and their I/O direction changes to the input direction. (The
pull-up resistor is disconnected regardless of the setting of the PCR Register.)