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SST89C54-33-AC-NI Datasheet(PDF) 11 Page - Silicon Storage Technology, Inc |
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SST89C54-33-AC-NI Datasheet(HTML) 11 Page - Silicon Storage Technology, Inc |
11 / 50 page 11 © 2000 Silicon Storage Technology, Inc. 344-2 8/00 FlashFlex51 MCU SST89C54 / SST89C58 Preliminary Specifications 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Activation and Deactivation of Memory Re-mapping The actual amount of memory that is re-mapped is controlled by MAP_EN[1:0] bits as shown in Table 2. The MAP_EN[1:0] bits are the same bits as SFCF[1:0]. The MAP_EN[1:0] bits are under software control and can be changed during program execution. Since changing re- mapping will cause program re-location, it is advisable that the instruction that changes the MAP_EN[1:0] be in the portion of memory that is not affected by the re- mapping change. The MAP_EN[1:0] bits are initialized at Reset according to the contents of two non-volatile register bits, Re- Map[1:0] (as shown in Table 2). The Re-Map[1:0] bits are programmed via PROG_RB1 and PROG_RB0 External Host Mode commands. Refer to External Host Program- ming Mode section for PROG_RB1 and PROG_RB0 commands. The contents of MAP_EN[1:0] are only updated accord- ing to Re-Map[1:0] on a successful reset. Any subse- quent alteration to the Re-Map[1:0] bits will not automati- cally change the MAP_EN[1:0] bits without a reset. Similarly, changes to MAP_EN[1:0] during program ex- ecution will not change Re-Map[1:0] bits. To deactivate memory re-mapping, a CHIP-ERASE op- eration will revert Re-Map[1:0] to the default status of “11”, disabling re-mapping. Programming 00b to SFCF[1:0] register also deactivates memory re-map- ping. The effect of programming Re-Map[1:0] is available only after the next reset. Refer to In-Application Mode Commands section for more detailed information. TABLE 2: RE-MAPPING TABLE Re-Map [1:0]1 MAP_EN2,3 Comments 11 00 Re-mapping is turned off. Program memory is in normal configuration. 10 01 1 KByte of flash memory location is re-mapped. Program access to location 0000h-03FFh is redirected to F000h – F3FFh. 01 10 2 KBytes of flash memory location are re-mapped. Program access to location 0000h-07FFh is redirected to F000h – F7FFh. 00 11 4 KBytes of flash memory location is re-mapped. Program access to location 0000h-0FFFh is redirected to F000h – FFFFh. 1 Re-Map[1:0] are nonvolatile registers which are examined only during Reset. 2 MAP_EN[1:0] are initialized according to Re-Map[1:0] during Reset. 3 MAP_EN[1:0] are located in SFCF[1:0], they determine the Re-Mapping configuration. They may be changed by the program at run time. 344 PGM T2.3 |
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