GoKawiilTarget: ti84plus.rom (1 MiB flash dump). OS self-identifies as 2.55MP. CPU: Zilog Z80 (16-bit address bus, 64 KiB logical space) with hardware flash/RAM paging. Ghidra project: ti84.gpr (rebuild: tools/build.sh ).
Confidence is flagged: [confirmed] = verified in disassembly/decompiler; [standard] = matches documented TI-83+/84+ architecture and is consistent with the disassembly; [hypothesis] = inferred, not yet verified.
The TI-84+ is a Z80 machine that can only see 64 KiB at once, but has 1 MiB of flash and 128 KiB of RAM. It bridges that gap with a 4-slot paging scheme and a system-call (“bcall”) mechanism that lets code on one 16 KiB flash page call routines on any other page. The OS is a single-tasking monitor: a boot/kernel core on flash page 0 (always mapped low), a large body of OS routines spread across the other flash pages and reached via bcalls, and a fixed RAM region holding the system state (flags, floating-point registers, display buffers, the variable table).
Everything the user interacts with — the homescreen, TI-BASIC programs, graphing, the catalog — is built on four pillars:
Paging + bcalls — how code and data beyond 64 KiB are reached. (see 02-paging.md, 03-bcall-mechanism.md) The floating-point engine — 9-byte BCD reals/complex in the OP1–OP6 registers; all math flows through these. (06-floating-point.md) The variable system (VAT) — named objects (reals, lists, matrices, strings, programs, appvars…) catalogued in the Variable Allocation Table. (05-variables-vat.md) The tokenizer/parser — TI-BASIC is stored as 1- and 2-byte tokens; the parser executes them. (07-tokenizer-basic.md)
Around those sit the I/O subsystems: the IM1 interrupt that drives timing/APD/cursor/ON-key (04-interrupts.md), the LCD driver, the keypad scanner, and the link port.
Each row maps a documentation page to the subsystem it covers and its analysis status.
Doc Subsystem 01-memory-map.md Address space, ports, RAM layout 02-paging.md Flash/RAM banking (ports 6/7) 03-bcall-mechanism.md rst 28h system calls + jump table 04-interrupts.md IM1 ISR, timers, APD, ON key 05-variables-vat.md Variable Allocation Table, object types 06-floating-point.md BCD float format, OP registers 07-tokenizer-basic.md Token tables, parser/interpreter 08-display-lcd.md LCD ports, screen buffers 09-keyboard-link.md Keypad scan, link protocol 10-subsystem-map.md bcall API surface, system through-line 11-boot-contexts-errors.md Boot, context system, _JError/onSP 12-memory-management.md RAM heap, VAT/userMem, Flash archive/GC 13-flash-page-map.md What each of the 64 flash pages contains 14-ram-pages.md RAM page selectors, page 83 , and restore rules 99-open-questions.md Prioritized future-work roadmap sub-calculation.md Calculation engine: FP ops, transcendentals, formatting, errors sub-graphing.md Graphing: window vars, coord↔pixel, draw primitives, Y= eval sub-tibasic.md TI-BASIC: program execution, control flow, I/O commands sub-tibasic-tracing.md TI-BASIC fixture traces, smoke runner, coverage anchors sub-vat-archive.md Variables, Sto/Rcl, Archive/Unarchive, Flash GC sub-apps-mem-settings.md Apps find/launch, RAM-reset, MODE/format flags sub-statistics.md STAT: 1/2-var, regressions, statVars sub-matrix-list.md Matrix/list element access, Gauss-Jordan inverse/det, matmul sub-solver-numeric.md Solver root-finder, nDeriv/fnInt, TVM finance sub-table-yvars.md TABLE generation/cache, Y= equation vars sub-equation-display.md Equation display / MathPrint layout (page 0x39 eqdisp_* ) sub-link-transfer.md Link protocol: byte/packet/var-transfer (page 0x3C) sub-usb-asic.md USB ASIC/link-assist ports and OS transport selection
(The sub-* docs are deep dives covering user-facing functionality and I/O internals: calculation, graphing, TI-BASIC, VAT/archive, apps, stats, matrices, solver, table, equation display, link, and USB/link assist.)
New to these notes? Start with Conventions & Methodology (how to read the addresses and confidence flags) and the Glossary; the bcall Index is the full alphabetical system-call reference.