Sharp's SM5xx MCUs were used in other things besides handheld toys. The manual for the PC-1600 Pocket Computer describes a 4-bit LU57813P processor, which looks like a SM578 type.
"The PC-1600 has three CPUs: two main CPUs and one sub-CPU. The two main CPUs are SC-7852 (equivalent to Z-80A: 3.58 MHz clock) and LH-5803 (equivalent ta LH-5801: 1.3 MHz clock). The sub-CPU is LU-57813P, which is a 4-bit CMOS processor af 307.2 KHz clock."
