128KB ARM Cortex-M3 Full-speed USB Device 72MHz
Directly compatible with STM32F103RBT6 code and hardware.
We had to subsitute in our hardware due to shortage in STM32 chips.
We used the same hex file as STM32F103RBT6 created in keil for testing and everything works.
We even debug this APM32 part with ST-LINK as STM32F103RBT6 device and it works.
Similar success we had for 48p device replacement so we went ahead with this 64p device as replacement.