SST89V54RD2 Silicon Storage Technology, Inc., SST89V54RD2 Datasheet - Page 11

• Manufacturer Part Number: SST89V54RD2
• Description: Flashflex51 Mcu
• Manufacturer: Silicon Storage Technology, Inc.

FlashFlex MCU
SST89V54RD2/RD / SST89V58RD2/RD
3.2 Program Memory Block Switching
The program memory block switching feature of the device allows either Block 1 or the lowest 8 KByte of Block 0 to be
used for the lowest 8 KByte of the program address space. SFCF[1:0] controls program memory block switching.
TABLE
3.2.1 Reset Configuration of Program Memory
Block Switching
Program memory block switching is initialized after reset
according to the state of the Start-up Configuration bit SC0
and/or SC1. The SC0 and SC1 bits are programmed via
an external host mode command or an IAP Mode com-
mand. See Table 4-2.
©2007 Silicon Storage Technology, Inc.
SFCF[1:0]
FIGURE
10, 11
01
00
3-1: SFCF Values for Program Memory Block Switching
FFFFH
0000H
3-2: Program Memory Organization for 32 KByte SST89x58RDx
Program Memory Block Switching
Block 1 is not visible to the PC;
Block 1 is reachable only via in-application programming from E000H - FFFFH.
Both Block 0 and Block 1 are visible to the PC.
Block 0 is occupied from 0000H - 7FFFH. Block 1 is occupied from E000H - FFFFH.
Block 1 is overlaid onto the low 8K of the program address space; occupying address locations 0000H -
1FFFH.
When the PC falls within 0000H - 1FFFH, the instruction will be fetched from Block 1 instead of Block 0.
Outside of 0000H - 1FFFH, Block 0 is used. Locations 0000H - 1FFFH of Block 0 are reachable through
in-application programming.
EA# = 0
64 KByte
External
DFFFH
FFFFH
E000H
7FFFH
1FFFH
8000H
2000H
0000H
SFCF[1:0] = 00
EA# = 1
24 KByte
24 KByte
External
8 KByte
8 KByte
Block 1
Block 0
Block 1
11
DFFFH
FFFFH
7FFFH
E000H
8000H
0000H
Once out of reset, the SFCF[0] bit can be changed dynam-
ically by the program for desired effects. Changing SFCF[0]
will not change the SC0 bit.
SFCF[1:0] = 01
EA# = 1
24 KByte
32 KByte
External
8 KByte
Block 1
Block 0
FFFFH
7FFFH
8000H
0000H
SFCF[1:0] = 10, 11
EA# = 1
32 KByte
32 KByte
External
Block 0
1255 F03.0
S71255-10-000
Data Sheet
T3-1.0 1255
12/07