3.3 I/O Pins Settings

Each I/O pin has an associated IOx settings register, which controls the following parameters for the associated I/O pin:

  • Pin function designation
  • Pin direction
  • Default output state
  • Pull-up enable or disable
  • Open-drain enable or disable
  • Alert edge selection or clock output frequency, where applicable

The supported settings for each I/O pin designation are shown in Table 3-2.

Table 3-2. I/O Designations and Other Pin Settings
I/O DesignationI/O DirectionOpen-DrainPin Output StatePull-upTrigger Edge/Clock frequency
GPIO [5:0]Input/OutputEnable/Disable (if output)‘0’/’1’ (if output)Enable/Disable (if input)—
ALRT [3:0]Input——Enable/DisableFalling, rising, both or none
CS [3:0]Output—SPI controlled——
CLKOOutput—Clock Module Controlled—6 MHz, 4MHz, 2MHz or 1MHz
USBCFGOutputEnable/DisableUSB controlled——
USBSPNDOutputEnable/DisableUSB controlled——
RTSOutputEnable/DisableUART controlled——
CTSInput——Disable—
RXAOutputEnable/DisableUART controlled——
TXAOutputEnable/DisableUART controlled——
SPIAOutputEnable/DisableSPI controlled——
I2CAOutputEnable/DisableI2C controlled——
I2CTOOutputEnable/DisableI2C controlled——
Table 3-3. I/O Pin Settings Map
Byte IndexRegister nameComments
0IO0SETTINGIO0 pin designation, direction, pull-up enable, open-drain, alert edge, and idle-state selection
1IO1SETTINGIO1 pin designation, direction, pull-up enable, open-drain, “—”, and idle-state selection
2IO2SETTINGIO2 pin designation, direction, pull-up enable, open-drain, alert edge, and idle-state selection
3IO3SETTINGIO3 pin designation, direction, pull-up enable, open-drain, CLKO frequency, and idle-state selection
4IO4SETTINGIO4 pin designation, direction, pull-up enable, open-drain, alert edge, and idle-state selection
5IO5SETTINGIO5 pin designation, direction, pull-up enable, open-drain, alert edge, and idle-state selection
The I/O pin power-up settings are made active settings during a device power-up or reset. Changes made to these settings take effect after:
  • A power cycle
  • A device Reset
  • Sending the vendor command, CNFG_SetNVMAsCurrent

The changes made to the active settings take effect immediately but are lost after a power cycle or a device reset.