The Cortex-M0 / Cortex-M0+ / Cortex-M1 / Cortex-M23 were designed to create the smallest silicon die, thus having the fewest instructions of the Cortex-M family. The Cortex-M0 / M0+ / M1 include Thumb-1 instructions, except new instructions (CBZ, CBNZ, IT) which were added in ARMv7-M architecture.