# What are the electrical specifications of the RGMII bus on SwitchBlox Rugged?

**URL:** <https://forum.botblox.org/t/what-are-the-electrical-specifications-of-the-rgmii-bus-on-switchblox-rugged/437>\
**Category:** BotBlox Hardware\
**Tags:** switchblox-rugged\
**Created:** [June 6, 2025, 10:45pm UTC](https://forum.botblox.org/t/what-are-the-electrical-specifications-of-the-rgmii-bus-on-switchblox-rugged/437 "2025-06-06T22:45:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![botblox\_admin](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.botblox.org/botblox_admin/32/1_2.png) [@botblox\_admin](https://forum.botblox.org/u/botblox_admin)\
**Post date:** [June 6, 2025, 10:45pm UTC](https://forum.botblox.org/t/what-are-the-electrical-specifications-of-the-rgmii-bus-on-switchblox-rugged/437/1 "2025-06-06T22:45:01Z")

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We would like to connect the RGMII port on SwitchBlox Rugged to another device via a cable. Can you provide some information on the electrical specifications of the RGMII port?

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**Author:** ![josh\_elijah](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.botblox.org/josh_elijah/32/568_2.png) [@josh\_elijah](https://forum.botblox.org/u/josh_elijah)\
**Post date:** [June 7, 2025, 6:41pm UTC](https://forum.botblox.org/t/what-are-the-electrical-specifications-of-the-rgmii-bus-on-switchblox-rugged/437/2 "2025-06-07T18:41:53Z")

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We haven’t officially tested whether this is possible, and RGMII isn’t really designed to be transmitted on cables very far. RGMII is very sensitive to skew between the clock and data signals, so if you are using a cable, it’s important to keep the cable short, and that the individual conductors in the cable are reasonably length matched.

Another issue is that the RGMII connector on SwitchBlox Rugged is not really designed to mate with a cable. It’s designed for board-to-board connections; specifically for mating two SwitchBlox Rugged boards together to form a 10 port switch. The part we use for the RGMII connector ([0873401824](https://www.digikey.com/en/products/detail/molex/0873401824/699229)) has a short pin depth and there is no retaining method on the board.

A cable like this ([TCMD-08-T-02.00-01-N](https://www.digikey.com/en/products/detail/samtec-inc/TCMD-08-T-02-00-01-N/1106719)) might work, it has male pins that can plug into the header on the board, but you’ll still need to figure out a way to keep the cable in place.

**RGMII Pinout**  
Below is the pinout of the header.

 ![image](https://canada1.discourse-cdn.com/flex027/uploads/botblox1/original/1X/c37216c4c514a7b1487488d9d636a34f82d1e4de.jpeg)

NC = Not connected  
RX pins are outputs from the board  
TX pins are input to the board.

**Electrical Specifications**  
Voltage level: 3.3V  
Clock frequency: 125MHz  
Ingress delay added to incoming TX clock = 0ns  
Exgress delay added to outgoing RX clock = 1.5ns

**Clock specifications**

 ![image](https://canada1.discourse-cdn.com/flex027/uploads/botblox1/original/1X/7db64af06bc0d681bb265cf1271b859e077180db.png)  
(Taken from the KSZ8567S datasheet)