Confirmed Compatibility Facts
The TI 520C CPU (Texas Instruments 505 series, later carried under Siemens SIMATIC TI505) supports user EPROMs for program storage. The verified part in hand is PPX2587681-8012, a 64K x 8 device (512 Kbit). An official EPROM part-number list was published in the product catalog, and the 520C/530C system manual contains a dedicated chapter on EPROM usage — including usage notes on its first page that should be read before installing any device. These two documents are the authoritative compatibility references; part numbers published only for the 525 or other later models should not be assumed valid for the 520C.
Interpreting the PPX2587681 Suffix
The evidence does not define what the suffixes (-8012, -8007, -8005) encode — memory size, firmware image revision, or device speed are all plausible, and the source material does not resolve which. Do not assume a lower suffix number means a smaller or compatible memory. The correct decision path: locate the catalog EPROM table and the 520C/530C manual chapter, and treat a suffix variant as compatible only if it appears in that published list for the 520C. A device with different organization than 64K x 8 will not be interchangeable regardless of suffix.
Verification Procedure Before Installation
- Obtain the EPROM chapter of the 520C/530C system manual and read its usage notes first.
- Cross-check the candidate part number (e.g., PPX2587681-8007 or -8005) against the catalog EPROM part-number list for the 520C specifically — not the 525 list.
- Confirm the device organization matches 64K x 8, matching the known-good PPX2587681-8012.
- Program the EPROM with the CPU's program image, install it per the manual chapter, and power up to verify the CPU loads and runs from EPROM.
Migration Consideration
Because the 520C is long out of production and even Siemens no longer distributes its manuals, a replacement with a CTI CPU is the recommended long-term path. However, for regulated or validated legacy equipment — such as the X-ray simulator in this case — keeping the existing CPU with a verified EPROM is a defensible decision. Retain the manual chapter and catalog extract with the machine documentation, since these references are no longer available through official channels.
Frequently Asked Questions
What EPROM part number works in a TI 520C CPU?
PPX2587681-8012, a 64K x 8 device, is confirmed for the 520C. Other variants must be cross-checked against the catalog EPROM list and the 520C/530C system manual EPROM chapter.
Can I use PPX2587681-8007 or -8005 instead of -8012 in a 520C?
Not without verification — the suffix meaning is not documented in the available evidence. Confirm the variant appears in the official catalog EPROM list for the 520C before substituting.
Are EPROM part numbers listed for the TI 525 valid for the 520C?
No assumption should be made. Use only the 520C/530C system manual's EPROM chapter and the catalog list specific to the 520C to confirm compatibility.