While 100Base-T1 was originally developed for automotive applications, its exceptional attributes and cost efficiency have also positioned it as a key enabler of Industry 4.0 and the Industrial Internet of Things (IIoT). Defined by the IEEE 802.3bp standard, 100Base-T1 supports 100 Mb/s data transmission specifically tailored for automotive environments. On the other hand, 100Base-TX, specified under the IEEE 802.3u standard, also delivers speeds of up to 100 Mbps but was designed primarily for traditional Ethernet networks.
At first glance, these two Ethernet standards might seem interchangeable due to their identical data transmission speeds. However, they are fundamentally different in several critical aspects, and assuming one can simply replace the other would be a mistake. This article aims to clarify the key similarities and differences between 100Base-T1 and 100Base-TX, providing you with the insights needed to make an informed decision for your specific application.
Graphic 1: 100Base-T1 vs. 100Base-TX
What led to the development of 100Base-T1?
Developed as the first automotive Ethernet standards by Broadcom under the name BraodR-Reach, 100Base-T1 was introduced as a replacement for the 100Base-TX commonly known as fast Ethernet in automotive1. This replacement was urgently needed because the 100Base-TX needs two twisted-pair cables and therefore doesn't adhere to the severe Comité International Spécial des Perturbations Radioélectriques (CISPR) 25 Class 5 radiation emissions standards. In need of an alternative, 100Base-T1 shifted the attention to an Ethernet standard specifically developed for automotives. Nevertheless, both Ethernet standards have a few features in common even though they also differ considerably.
What makes 100Base-T1 similar to 100Base-TX?
Both provide full-duplex data transmission at 100 Mbit/s via unshielded twisted pairs of Category 5 (Cat5) or above cables for data transmission to minimize electromagnetic radiation and crosstalk impact on other cables.
Differences between 100Base-T1 and 100Base-TX?
Despite 100Base-TX fast Ethernet being identical to its automotive counterpart the 100Base-T1 in terms of speed (100Mbps), these two differ significantly as summarized in Table 1.
| In terms of: | 100Base-T1 | 100Base-TX |
| Cables usage | single twisted pair of unshielded cables | two twisted pairs of unshielded cables |
| Maximun distance | 15m between end nodes | 100m between end nodes |
| Full Duplex transmission | A single pair of cables for both data transmission and reception | One pair of cables is used for data transmission, the other is used for data reception |
| Connectors used | Numerous types including M8, M12 amongst others | RJ-45 |
| Cost | Cheaper | more Expensive |
| Intended application | Automotive | Industrial |
Table 1: Differences between 100Base-TX and 100base-T1
Conclusion
100Base-T1 stands out as the leading automotive Ethernet standard, specifically designed to meet the rigorous demands of modern vehicle networks. Built on insights gained from 100Base-TX and other conventional Ethernet standards, 100Base-T1 has been carefully optimized for automotive applications, delivering reliable performance in challenging environments. However, as the need for even higher data speeds and lower latency continues to grow, 100Base-T1 is challenged to meet current industrial standards. Therefore, the industry has introduced 1000Base-T1—a next-generation standard developed to address evolving requirements.
