Flash

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The Casio Prizm uses the NOR Flash chip for storing boot code and OS update code, the OS itself, as well as the Storage Memory. The flash chip is much slower than the RAM, but is 16 times larger.

Hardware Specs

The Prizm traditionally included a Spansion flash chip, until hardware revision 001V04, when it was replaced by a Macronix chip. Possible reasons for the replacement include the fact that the Spansion part was discontinued, a lower price on the Macronix part, and/or the fact that at higher input voltages, the Macronix part has slightly lower access times (90 ns vs. 100 ns).

For some reason, calculators with the Macronix chip (or is it because of HW version 4?) take about a second longer to cold-boot than older calculators.

OS 02.00 includes support for both Spansion and Macronix flash. A special version of OS 01.04 shipped with hardware version 001V04, possibly to add support for Macronix flash (this version was not available for download). The Spansion and Macronix flash chips in question are almost 100% compatible, and the differences do not seem to be relevant to the basic flash operations. It is not known whether OS versions older than the special 01.04 are able to run on hardware with the Macronix part.

Spansion

  • Manufacturer: Spansion
  • Model No.: S29GL256N10TFI02
  • Size: 256 Megabits / 32 MB
  • Speed: 100ns
  • Package: TSO56
  • Lead free
  • Temp. Rating: -40°C to 85°C
  • Power: 2.7V to 3.6V
  • Protection: Protection features available, but not used on the Prizm (first sector is writable).

Macronix

  • Manufacturer: Macronix
  • Model No.: MX29GL256FLT2I
  • Size: 256 Megabits / 32 MB
  • Speed: 100ns (VCC=2.7~3.6V), 90ns (VCC=3.0~3.6V)
  • Package: TSO56
  • Halogen free
  • Temp. Rating: -40°C to 85°C
  • Power: 2.7V to 3.6V
  • Protection: Protection features available, but not used on the Prizm (first sector is writable).

Memory Mapping

The Prizm maps the actual flash chip in a few locations. Firstly, there are two direct access locations available to access the entire flash:

  • 0xA0000000 to 0xA1FFFFFF - Cached
  • 0x80000000 to 0x81FFFFFF - Same, but non-cached

Addins are executed from the ROM, with the executable code virtually mapped to 0x00300000 by the MMU.

Mapping files to memory

Some work has been done to develop a way to map storage memory files to addresses in the memory space, similarly to the way add-ins are mapped. Such development should be considered alpha-stage; it has been paused due to a (possibly unrelated) hardware failure. More information in AHelper's GitHub project: https://github.com/AHelper/ld-prizm

Reading Files Directly

See the Using the File System tutorial and look at using the Bfile_FindFirst function to get the direct address for files.

Formatting and Mounting

Todo.

OS Updating

Todo. Uses Protocol 7 to load flashing payload to RAM, then receives OS.


Special thanks to Simon Lothar for his documentation and for anyone else involved.