Renesas’ RL78/L12 MCUs

Image via Renesas

Generally, embedded applications call for an LCD screen to update the user on how the programs are running, to notify of errors, or to indicate the response to a command. Renesas’ RL78/L12 MCUs contain on-chip LCD drivers/controllers. This allows usage for industrial and consumer devices that need a quick and low-power visual interface MCU.

The RL78/L12 MCUs have a 1.6 to 5.5-V operation from a single supply. These MCUs consume 75 μA/MHz in active mode, 0.64 μA in halt mode, and 0.23 μA in stop mode. The LCD circuit increases by 0.61 μA from the internal voltage boost. The RL78/L12 slightly resembles the RL78/L13, since it has a program flash ranging from 8 to 32 Kbytes, SRAM of 1 to 1.5 Kbytes, and data flash of 2 Kbytes. 

The chips have a 16-bit RL78 RL78 CPU core that supplies 31 DMIPS at maximum operating speed of 24 MHz. CISC architecture is included with a three-stage pipeline. There is a 16 x 16 to 32-bit result for one clock cycle, where 86% of instructions can be executed in one to two clock cycles. The 16-bit barrel shifter for shift and rotate in one clock cycle. The code flash memory is from 8 to 32 Kbytes. There is an on-chip single-voltage flash memory with protection from block erasing and overwriting.

Data flash memory of this microcontroller works with background operations, while the total data flash size is 2 Kbytes of data. The RAM comes in either 1 or 1.5 Kbytes, and backup retention is available in all modes. The high-speed on-chip oscillator has 24 MHz with ±1% accuracy over voltage (1.8 to 5.5 V) and temperature (–20º to 85ºC). 24 MHz, 16 MHz, 12 MHz, 8 MHz, 4 MHz, and 1 MHz are the standard settings for the RL78/L12, and a low-voltage detector keeps the user informed.

The LCD driver is crucial in distinguishing this device in the marketplace, supporting up to 280 LCD segments and 16 levels of contrast. The pincount and RAM size are then chosen to match the display size. Internal voltage boosts, capacitor splits, and external resistance divisions can be supported on the chip, where the display drive voltage comes from. 

Story via Renesas