{"id":139990,"date":"2026-08-31T04:21:33","date_gmt":"2026-08-31T11:21:33","guid":{"rendered":"https:\/\/www.stevenrhine.com\/?p=139990"},"modified":"2026-08-31T04:21:33","modified_gmt":"2026-08-31T11:21:33","slug":"teardown-datum-9390-gps-time-code-and-frequency-generator","status":"publish","type":"post","link":"https:\/\/www.stevenrhine.com\/?p=139990","title":{"rendered":"Teardown Datum 9390 GPS Time Code and Frequency Generator"},"content":{"rendered":"

Teardown Datum 9390 GPS Time Code and Frequency Generator<\/p>\n

\"\"<\/a>
\nCover Off
\n\"\"<\/a><\/p>\n

Firmware Archive<\/p>\n

Datum 9390 GPS EPROM ARCHIVE<\/a>
\n27C2048 PLCC (256KB) is the firmware for the GPS receiver engine itself. Two things confirm this:<\/p>\n

Its byte pairs swapped from true memory order (a common artifact of dumping a 16\u2011bit\u2011wide part with certain EPROM programmers). Un-swapping it exposes a clean copyright string: Copyright (C) 1992,1993 Trimble Navigation Written by Paul Braisted, plus a long run of GPS-engine debug strings (Signal Processor error:, Blind search, Tracking set update, SVs visible, Different week, etc).<\/p>\n

Datum 9390 DDISPLAY EPROM ARCHIVE<\/a>
\nM27C1001 DIP (128KB) is the front-panel keypad\/LCD controller separate MCU, plain 8-bit ASCII, no swap needed. It’s full of UI prompt strings (ENTER LATITUDE:, ENTER TIME, DOING GPS CORRECTION, GPS TIME NOT ACQUIRED, etc.)<\/p>\n

SRAM M48Z35Y ARCHIVE<\/a><\/p>\n

X-Ray of M48Z350Y<\/p>\n

\r\n
\r\n \r\n <\/i>\r\n <\/a>\r\n 0 <\/span>\r\n<\/div>
\r\n \r\n <\/i>\r\n <\/a>\r\n 0<\/span>\r\n<\/div><\/div>","protected":false},"excerpt":{"rendered":"

Teardown Datum 9390 GPS Time Code and Frequency Generator Cover Off Firmware Archive Datum 9390 GPS EPROM ARCHIVE 27C2048 PLCC (256KB) is the firmware for the GPS receiver engine itself. Two things confirm this: Its byte pairs swapped from true memory order (a common artifact of dumping a 16\u2011bit\u2011wide part with certain EPROM programmers). Un-swapping […]<\/p>\n","protected":false},"author":1,"featured_media":139991,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"","_lmt_disable":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-139990","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-stevens-posts"],"yoast_head":"\nTeardown Datum 9390 GPS Time Code and Frequency Generator - Steven Rhine - Rhine Labs Blog \/ News<\/title>\n<meta name=\"description\" content=\"Teardown Datum 9390 GPS Time Code and Frequency Generator, Firmware Backup and More..\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.stevenrhine.com\/?p=139990\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Teardown Datum 9390 GPS Time Code and Frequency Generator\" \/>\n<meta property=\"og:description\" content=\"Teardown Datum 9390 GPS Time Code and Frequency Generator, Firmware Backup and More..\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.stevenrhine.com\/?p=139990\" \/>\n<meta property=\"og:site_name\" content=\"Steven Rhine - 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