SM89516B datasheet(19/49 Pages) SYNCMOS

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SM89516B

8-Bit Micro-controller

64KB Flash

& 1KB RAM embedded

Specifications subject to change without notice contact your sales representatives for the most recent information.

ISSFD-M087

Ver D SM89516B 08/07/2015

- 19 -

Mnemonic: SCONF

Address: BFh

Reset

WDR

PDWUE

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

Reset

RAMS1

RAMS0

00H

OME

RAMS1

RAMS0

Mapped on-chip expanded RAM address

Note

$0000 - $00FF

$0100 - $01FF

$0200 - $02FF

Mapped to off-chip RAM

address {P2 , Ri}

Mapped to off-chip RAM

address {P2 , Ri}

Table 3-1 : Mapped address for on-chip expanded RAM

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