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**Gene** · (This post was last modified: 02-25-2024 12:06 AM by Gene.)

From Joerg at Datamath.org. Posted here by request

TI-5230 – The big brother of the TI-59 or the little sister of the SR-60?

http://www.datamath.org/Desktop/ti-5230.htm

A friend of mine who is for whatever reasons not on the HP Museum Forum managed recently not only to repair a broken TI-5230 (dim display, printer chip burnt) but started to reverse-engineer it.

While the TI-5230 looks inside at first glance like a SR-60, is it using a VF-Display instead the Dot-Matrix display – and there are no TMC0500 Building Blocks (the genius architecture behind TI classics from SR-51 to TI-59) for VF-Displays!

Well, digging deeper into the TI-5230 reveals a TMS1300 single-chip calculator chip driving the display and a TMC0250 Printer Controller (known from PC-100 and SR-60) for the Thermal Printer. While the TMC0250 is connected to the serial bus of the TMC0501E, couldn’t he imagine a way how a TMC0501E communicates with the TMS1300 with only “Key-Scanning” capabilities.

Well, many hours later after probing the signals, dumping the TMC0501 ROMs (this beast has 6k ROM like the TI-59 and more than double its RAM) and looking into the Constant-ROM of one of the Chips, we finally understand: TI developed a simple protocol with sending 17 BCD “commands” from the Constant-ROM of the TMC0587 SCOM Chip (Scanning ROM – doesn’t scan the display obviously) to the Keyboard Inputs of the TMC1376 Chip which “debounces” the commands, interprets them and sets the display accordingly.

Well, the TMC1376 single-chip calculator chip is sort of compatible with the DCM-50A Platform my friend is using to reverse-engineer calculators from the Seventies and bypassing the keyboard with a few jumpers and stimulating the four Keyboard-Inputs with an FPGA running the 17 BCD commands that a TMC0501E would send, proved his interpretation of the protocol.

To complete his research he would now need a copy of the programming manual – the SET UP, DR and CR keys are everything but intuitive….

http://datamath.net/TI-5230.jpg

http://datamath.net/TMC1376.jpg