# \[Hilo\] How do RTS-CTS work for hardware flow control?

**URL:** <https://forum.sierrawireless.com/t/hilo-how-do-rts-cts-work-for-hardware-flow-control/6501>\
**Category:** HL Series FAQ\
**Created:** [July 19, 2013, 6:32am UTC](https://forum.sierrawireless.com/t/hilo-how-do-rts-cts-work-for-hardware-flow-control/6501 "2013-07-19T06:32:15Z")\
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**Author:** ![FAQ\_Poster](https://avatars.discourse-cdn.com/v4/letter/f/f9ae1b/32.png) [@FAQ\_Poster](https://forum.sierrawireless.com/u/FAQ_Poster)\
**Post date:** [July 19, 2013, 6:32am UTC](https://forum.sierrawireless.com/t/hilo-how-do-rts-cts-work-for-hardware-flow-control/6501/1 "2013-07-19T06:32:15Z")

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[Hilo] What’s the RTS-CTS connection? How does it work when in H/W flow control?

Answer: CTS\_HILO is an output from HILO and an input to RTS\_HOST. HILO uses CTS to signal HOST to stop sending.  
CTS\_HOST is an output from HOST and an input to RTS\_HILO. HILO stops sending to HOST when it sees that RTS is asserted

For example, seen from HILO:  
1/ CTS\_HILO is managed by HILO:

- When CTS\_HILO is on active level (low electrical level), that means that HOST (your uC) can send.
- If CTS\_HILO is on inactive level (high electrical level), that means that HOST must stop sending.

2/ RTS\_HILO is managed by the HOST:

- If RTS\_HILO is set to the active level (low electrical level), HILO can send.
- If RTS\_HILO is set to the inactive level (high electrical level), that means that HILO must stop sending.