80 MHz Cortex-M3 with 256 KB Flash — what the memory ratio means for firmware fit
The LM3S1R21-IBZ80-C3T runs an ARM Cortex-M3 core at 80 MHz, with 256 KB of Flash and 48 KB of SRAM on-chip. That 5.3:1 Flash-to-RAM ratio is typical for a control-oriented MCU — the firmware image, including a real-time operating system kernel and communication stacks (TCP/IP, USB, CAN), fits in the Flash, while the SRAM handles the stack and data buffers without external memory.
Texas Instruments has marked the LM3S1R21-IBZ80-C3T as Obsolete. For a BOM line that already carries this order code, the sourcing posture is quoted-to-order against the required volume.
With 67 general-purpose I/O and a peripheral set that includes EBI/EMI, I²C, SPI, SSI, UART/USART, IrDA, LINbus, and Microwire, this MCU can interface directly with parallel LCDs, serial sensors, motor encoder interfaces, and LIN-based automotive subnets without a port expander or protocol translator. The 8-channel 10-bit ADC samples analog inputs for current sensing or temperature monitoring on the same die.
Package — 108-ball BGA layout constraints
Supplied in a 108-LFBGA with a 10x10 mm body and 0.80 mm ball pitch. The tight pitch demands at least a 4-layer PCB for fan-out of the inner balls to via-in-pad or dog-bone traces.