SM89516B
8-Bit Micro-controller
64KB Flash
& 1KB RAM embedded
Mnemonic: SCONF
Address: BFh
7
6
-
5
-
4
3
-
2
-
1
0
ALEI
Reset
02H
WDR
PDWUE
OME
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
00H
RAMS1 RAMS0
OME
RAMS1
RAMS0
Mapped on-chip expanded RAM address
$0000 - $00FF
Note
1
1
1
0
0
1
0
1
0
$0100 - $01FF
$0200 - $02FF
Mapped to off-chip RAM
address {P2 , Ri}
Mapped to off-chip RAM
address {P2 , Ri}
1
0
1
x
1
x
-
-
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-M087 Ver A SM89516B 3/7/2014
- 19 -
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
