Pin Control and Pin Function Selection (LPC40xx)
Learn about the selectable features of pins in the LPC40xx MCU, how to enable/disable these features and how to, select a pin's functionality.
The LPC40xx series chips have pins with the following features
see chapter Chapter 6: LPC408x/407x Pin configuration & Chapter 7: LPC408x/407x I/O configuration
Figure 1. I/O configurations Signals Highlighted (UM10562 LPC40xx Page 122)
- Open Drain Enable: Enabling this disables the high side MOSFET in of the totem pole configuration, making that pin an open drain.
Pin Modes (Only one or none of these can be active at once)
- Pull-Up Enable:Enabling this turns on the weak pull-down MOSFET in the ohmic region.
- Pull-Down Enable: Enabling this turns on the weak pull-down MOSFET in the ohmic region.
- Repeater Mode Enable: Enabling this, will activate the pull up or pull down resistor from the last.
- Enable Input Invert: Converts a pin configured as an input to active low.
- Enable Glitch Filter: Enables the 10nS glitch filter.
- Enable Analog Input: Disables schmitt trigger and enables voltage to pass through analog switch to analog input.
- There are actually more controls then this depending on the pin type you are using.
Figure 2. Type D IOCON registers (page 132)