SM8958B Datasheet, PDF (19/49 Pages) SyncMOS Technologies,Inc – 256 bytes SRAM as standard 8052

Mnemonic: SCONF
7
6
5
4
3
WDR
-
-
PDWUE
-
SM8958B
8-Bit Micro-controller
32KB Flash
& 1KB RAM embedded
Address: BFh
2
1
0
Reset
-
OME
ALEI
02H
OME: On-chip 768B expanded RAM enable bit.
Set 1 to enable on-chip 768B expanded RAM access.
There are two methods to access on-chip 768 bytes of expanded RAM. The first one is to use MOVX instruction
either by MOVX @DPTR or by MOVX @Ri. The other is to use a specific addressing bank switching scheme
combined with direct addressing MOV instruction.
Method 1 : By MOVX instruction
The 768 bytes on-chip expanded RAM can be accessed by MOVX instruction with OME bit in SCONF register
enabled. If MOVX @DPTR is used, the address range larger than 768B will force to access external data memory
automatically. If OME is disabled, IC will always access external data memory. OME is 1 in default setting.
The 768 bytes of on-chip expanded RAM can also be accessed by MOVX @Ri instruction. The content in Ri is
concatenated with RAMS1 and RAMS0 bit in RCON register in order to address on-chip 768bytes expanded RAM
and off-chip RAM totally up to 64KB memory range.
RAMS1 and RAMS0 bit in RCON register is the 256B bank selection while using MOVX @Ri to access expanded
RAM once OME bit in SCONF register is set.
Mnemonic: RCON
Address: 85h
7
6
5
4
3
2
1
0
Reset
-
-
-
-
-
-
RAMS1 RAMS0 00H
OME
1
1
1
1
0
RAMS1
0
0
1
1
x
RAMS0 Mapped on-chip expanded RAM address
Note
0
$0000 - $00FF
1
$0100 - $01FF
0
$0200 - $02FF
1
-
Mapped to off-chip RAM
address {P2 , Ri}
x
-
Mapped to off-chip RAM
address {P2 , Ri}
Table 3-1 : Mapped address for on-chip expanded RAM
Specifications subject to change without notice contact your sales representatives for the most recent information.
ISSFD-M085
Ver D SM8958B 08/07/2015
- 19 -