> 3.5.5 | Signal States after Startup

> Table 9 describes the various states each interface pin passes through after startup and during operation.
> The state of several pins will change again once the respective interface is activated or configured by AT command.

> Table 9: | Signal states

> Signal name | Undefined state during startup | Defined state after initialization | Active state after configuration by AT command
> GPIO | SPI | I 2C
> RXD | O, L | O, L |  |  |
> TXD | I | I |  |  |
> CTS | O, H | O, H |  |  |
> RTS | I | I |  |  |
> DTR | I | I |  |  |
> DCD | O, H | O, L |  |  |
> DSR | O, H | O, L |  |  |
> RING | O, L | O, L |  |  |
> SPIDI | I | Tristate |  | I | Tristate
> SPICS | I | O, H |  | O, L | Tristate
> I2CDAT_SPIDO | I | Tristate |  | O, L/H | IO
> I2CCLK_SPICLK | I | Tristate |  | O, L/H | O, OD
> IO1 | I, PU | Tristate | IO |  |
> IO2 | I, PU | Tristate | IO |  |
> IO3 | I, PU | Tristate | IO |  |
> IO4 | I, PD | Tristate | IO |  |
> IO5 | O, L | Tristate | IO |  |
> IO6 | I, PU | Tristate | IO |  |
> IO7 | I, PU | Tristate | IO |  |
> IO8 | O, L | Tristate | IO |  |
> IO9 | I | Tristate | IO |  |
> IO10 | I | Tristate | IO |  |

> Abbreviations used in Table 9:

> L = Low level H = High level L/H = Low or high level I = Input | O = Output OD = Open Drain PD = Pull down with min +15µA and max. +100µA PU = Pull up with min -15µA and max. -100µA