As consumer devices keep getting smaller and smaller, so too must the devices inside them. With that in mind Renesas has just introduced the RL78/G10 product line in a tiny 10- and 16-pin pin SSOP packages with 1-4 KB of Flash memory and 128-512 Kbytes of RAM. In the process they also reduced the operating current by 30% from that of the RL78/G13 (66 µA/MHz @ 32 MHz) to 46 µA/MHz (@ 20 MHz).
While these are slimmed down RL78s they’re still highly capable. Even the smallest chips incorporate a 2-channel 16-bit timer array unit (TAU); a 4-channel 10-bit ADC; a 4-level interrupt controller; a 12-bit interval timer that can serve as a trigger for waking up from STOP and HALT modes; and a high-speed on-chip oscillator (20/10/5/2.5/1.25 MHz). Serial interfaces include UART and simplified I2C; the 16-pin devices also include one channel of I2C and one or two CSI channels. Minimum instruction execution time can be changed from high speed (0.05 μs @ 20 MHz operation) to low speed (0.8 μs @ 1.25 MHz operation).
The RL78/G10 has the RL78-S1 core, a CISC architecture with a 3-stage pipeline, 1 MB of address space, and a general purpose register (8-bits x 8). The RL78-S2 core shares all instructions with the RL78-S1 core, though there are several instructions that require a different number of clock cycles. Check the preliminary RL78/G10 User’s Manual for more details.
Target applications for the RL78/G10 family are space-constrained portable consumer devices such as electric toothbrushes and razors, which used to get along with just on/off switches. Aside from always wanting longer battery life, according to the press release “finer control is now required in these products.”
In the case of my electric razor I’ve always thought the on/off switch worked pretty well. However, my daughter has multi-speed electric toothbrush that also plays different tunes while she’s brushing. I guess I could even see it having a “shuttle” option like her iPod—requiring her to brush her teeth longer to finish a song. Once I finish this blog post I intend to do a teardown (and hopefully reassembly) to see how it works. Who would have thought you’d need an MCU to control your toothbrush? Time marches on!