50 MHz ARM Cortex-M3 with integrated Ethernet — what this chip is
The 46 GPIOs in a 100-LQFP package give enough headroom for control panels and sensor aggregation boards.
The LM3S6911-EQC50-A2T carries an official obsolete status. Texas Instruments ended production on the Stellaris line after the acquisition; no last-time-buy window remains open. If you're maintaining a legacy board that uses this part, the only channel is the independent surplus market.
256 KB Flash / 64 KB SRAM — memory budget for the design
The 256 KB program Flash and 64 KB SRAM were generous for its era, enough to run a lightweight TCP/IP stack alongside a control loop. The 64 KB SRAM is shared between code data and Ethernet buffers — if your application pushes near that limit, a replacement with 128 KB or more SRAM gives breathing room. The Flash is not large by modern standards; firmware updates over Ethernet need careful sector management.
Ethernet on-chip — the feature that defined it
It supports 10/100 Mbps with an internal oscillator, so no external crystal for the Ethernet clock. If your replacement candidate lacks an internal PHY, budget for an external chip like the LAN8720 or KSZ8081 and the extra routing.