Hl7800 Maximum logic high voltage on UART pin

I am looking for maximum allowed logic high voltage for HL7800 on UART pins, I am trying to interface HL7800 to a controller which got logic high voltage level as 3.3v, need to know the maximum allowed voltage on RX,TX,CTS and RTS pins only.

Hi @infoeugine,

According to the document, the maximum allowed voltage on the RX, TX, CTS and RTS pins is 1.8V (VGPIO).
For more detail, you can refer to Table 3-3: Digital I/O Electrical Characteristics (1.80V) on page 27 and
Table 4-7: UART1 Pin Description on page 46.

The attached document below:
Sierra Wireless™ HL78xx Product Technical Specification