Application Note
3 of 19
001-87564 Rev.*D
2021-06-01
A Design Guide to SPI F-
RAM™ Processor Companion
- FM33256B
Two Logical Devices in One
r e s t r i c t e d
2
Two Logical Devices in One
Even though FM33256B is a single device, it is internally organized as two logical devices as shown in
Figure 1
Two Logical Devices with Unique Opcodes
The memory is one logical device, and the companion/RTC is the other logical device. This helps to integrate
both the functionalities without affecting each other. Each has its own address space and is accessed via the
SPI. The F-RAM is accessed through the standard memory opcodes (0x02 for Write and 0x03 for Read). The
processor companion/RTC is accessed through special opcodes (0x12 for Write and 0x13 for Read).
Note:
For the complete list of opcodes, refer to
