TI-86 RAM LayoutTI-86 RAM LAYOUT ---------------- MEMORY RAM MAP -------------- 0000h ------------------------- (ASIC) | | | ROM PAGE 0 | | | 4000h |-------------------------| | | | SWAPPED ROM PAGE(1-F) | | | 8000h |------------------------ | | | | SWAPPED RAM PAGE (1-7)| | | C000h |-------------------------| | | | STATIC RAM PAGE (0) | | | ------------------------- RAM PAGE 0 (16k) - not paged 0C000h ------------------------- (ABS) | | | system memory | | | |-------------------------| | INTER BANK RAM CACHE | |-------------------------| | RESEVERED RAM FOR | | ASSEMBLY LANGUAGE | | PROGRAMMING ~ 8k | |-------------------------| | ^ | | : | | hardware stack | RAM PAGES 2 - 7 (96K) 0FC00h |-------------------------| 14000 ------------------------- | display ram | (ABS) | USER MEMORY | 0FFFFh ------------------------- | | | | v | RAM PAGE 1 (16K) |.........................| 10000 ------------------------- FPBASE | TEMP MEMORY | (ABS) | floating point stack | | | | | : | | v | | v | |.........................| --- | . . . . . . . . . . . . | *FPS | ^ | 1 | | | | | | 6 | | FREE EXEC RAM | | TEMPS SYM TABLE | K | | . . . . . . . . . . . . | *OPS |.........................| | | ^ | | ^ | M | | : | | | | A | | operator stack | | USER SYM TABLE | X | 13FFF ------------------------- OPBASE ------------------------- ---- (ABS) - The TI-86 uses a paged RAM design inorder to allow the system to use more than 32k of RAM. - 16k of RAM at C000h - FFFFh is static RAM that is always directly addressable. - The 16k address space at 8000h - BFFFh is used for swapping in 1 of 7 other 16k RAM pages. - For ease of coding the RAM swapping was made transparent by overlaying an 'absolute address' space over the RAM pages. - Below is a chart showing how the absolute address is decoded into a RAM PAGE and an offset. ABS = ABSOLUTE ADDRESS ABS RAM PAGE ASIC ADDR ---- -------- --------- 0C000-0FFFF 0 C000-FFFF - always available 10000-13FFF 1 8000-BFFF - these are all paged 14000-17FFF 2 8000-BFFF 18000-1BFFF 3 8000-BFFF 1C000-1FFFF 4 8000-BFFF 20000-23FFF 5 8000-BFFF 24000-27FFF 6 8000-BFFF 28000-2BFFF 7 8000-BFFF - Some results from implementing a paged RAM system : - all memory accesses and moves involving paged RAM cannot be done directly, system routines are required to handle these operations. - loss of efficiency. - a 3 byte address must be used instead of 2 byte. TI-86 Assembly Programming |
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