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© 2000 Silicon Storage Technology, Inc.

344-2 8/00

FlashFlex51 MCU

SST89C54 / SST89C58

Preliminary Specifications

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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.

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