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telephony:td816bx_hardware

**This is an old revision of the document!**

Panasonic KX-TD816BX Hardware Insights

Overview

This system got not more than a few hundred KB's of RAM. System configuration is stored on a EEPROM. The CPU is a 68k chip (yeah, same as Macintosh computers and several embedded devices of the era). This unity got the TMP68301AF-12 variant of that chip, manufactured by Toshiba.

The ROM complex is detachable, for reasons I deem unclear, since those chips are already seated on sockets. See below for more information on that detachable board.

ROM/RTC clock Board

This complex seems to be upgradeable (if you ever find that stuff.) Here we can find:

  • IC20: P401A, matches the system ROM version (P401A60905A), so it's probably the main firmware;
  • IC21: P402A, Google returns nothing useful, unknown ROM chip;
  • IC24: CXK581000AP-10LL, or 131072-word × 8-bit High Speed CMOS Static RAM, which seems to provide our system with healthy 128 KB;
  • IC25: idem, bringing the total amount of RAM in this module to 256 KB;
  • IC26: OKI M6242B, an RTC clock chip;
  • X2: 32.768 kHz crystal oscillator for the RTC chip;
  • BAT: CR2354 battery, 3V, probaly of the /1GUF variant.

Problems

  • The RTC battery is probably long dead and showing signs of oxidation on it's legs;
  • There's was a bad and mysterious corrosion under the RTC oscillator, that I've already removed, after taking this photo;
  • This same oscillator isn't operating reliably, sometimes it takes a while for the clock to start, well, clocking, and this component is probably the culprit;
telephony/td816bx_hardware.1743692344.txt.gz · Last modified: 2025/04/03 11:59 by prppedro