CHAPTER 12: I/O Port
FM4 Peripheral Manual, Doc. No. 002-04856 Rev. *E 735
[bit3:2] MAINXC: Main Clock (Oscillation) Pin Setting Register
These bits set a pin as a main clock (oscillation) pin.
Reads out the register value.
Does not use two pins of X0 and X1 as main clock (oscillation) pins but as digital input/output
pins.
Uses two pins of X0 and X1 as main clock (oscillation) pins. [Initial value]
(An I/O cell will be in a state of input direction, input cut-off, and pull-up disconnection.)
Uses X0 pin as an external clock input pin.
Uses X1 pin as a digital input/output.
[bit1:0] SUBXC: Sub Clock (Oscillation) Pin Setting Register
These bits exist in TYPE5-M4 products.
These bits set a pin as a sub clock (oscillation) pin.
Reads out the register value.
Does not use two pins of X0A and X1A as sub clock (oscillation) pins but as digital
input/output pins.
Uses two pins of X0A and X1A as sub clock (oscillation) pins. [Initial value]
(An I/O cell will be in a state of input direction, input cut-off, and pull-up disconnection.)
Uses X0A pin as an external clock input pin.
Uses X1A pin as a digital input/output.
These bits do not exist in products other than TYPE5-M4.
0b01 is read from these bits.
When writing these bits, set them to 0b01.
Notes:
− Only writing 01 to the MAINXC bit does not make a main clock start oscillation.
To start oscillation, enable oscillation by the MOSCE bit of the System Clock Mode Control
Register (SCM_CTL), which is described in the chapter Clock, after writing 01 to the MAINXC bit.
− In TYPE5-M4 products, only writing 01 to the SUBXC bit does not make a sub clock start
oscillation. To start oscillation, enable oscillation by the SOSCE bit of the System Clock Mode
Control Register (SCM_CTL), which is described in the chapter Clock, after writing 01 to the
SUBXC bit.
In the products other than TYPE5-M4, for procedures of enabling the oscillation of sub-clock, see
Chapter Clock.
− This register is not initialized by deep standby transition reset.
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