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| 型号： | SST89E554A-40-C-NJ |
| 厂商： | SILICON STORAGE TECHNOLOGY INC |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8-BIT, FLASH, 40 MHz, MICROCONTROLLER, PQCC44 |
| 封装： | PLASTIC, MS-018AC, LCC-44 |
| 文件页数： | 5/87页 |
| 文件大小： | 996K |
| 代理商： | SST89E554A-40-C-NJ |
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Preliminary Specifications
FlashFlex51 MCU
SST89E554A / SST89V554A
13
2003 Silicon Storage Technology, Inc.
S71228-00-000
6/03
3.4 Expanded Data RAM Addressing
The SST89E/V554A both have the capability of 1K of
RAM. See Figure 3-2.
The device has four sections of internal data memory:
1. The lower 128 Bytes of RAM (00H to 7FH) are
directly and indirectly addressable.
2. The higher 128 Bytes of RAM (80H to FFH) are
indirectly addressable.
3. The special function registers (80H to FFH) are
directly addressable only.
4. The expanded RAM of 768 Bytes (00H to 2FFH) is
indirectly addressable by the move external
instruction (MOVX) and clearing the EXTRAM bit.
Since the upper 128 bytes occupy the same addresses as
the SFRs, the RAM must be accessed indirectly. The RAM
and SFRs space are physically separate even though they
have the same addresses.
When instructions access addresses in the upper 128
bytes (above 7FH), the MCU determines whether to
access the SFRs or RAM by the type of instruction given. If
it is indirect, then RAM is accessed. If it is direct, then an
SFR is accessed. See the examples below.
Indirect Access:
MOV@R0, #data; R0 contains 90H
Register R0 points to 90H which is located in the upper
address range. Data in “#data” is written to RAM location
90H rather than port 1.
Direct Access:
MOV90H, #data; write data to P1
Data in “#data” is written to port 1. Instructions that write
directly to the address write to the SFRs.
To access the expanded RAM, the EXTRAM bit must be
cleared and MOVX instructions must be used. The extra
768 bytes of memory is physically located on the chip and
logically occupies the first 768 bytes of external memory
(addresses 000H to 2FFH).
When EXTRAM = 0, the expanded RAM is indirectly
addressed using the MOVX instruction in combination
with any of the registers R0, R1 of the selected bank or
DPTR. Accessing the expanded RAM does not affect
ports P0, P3.6 (WR#), P3.7 (RD#), or P2. With
EXTRAM = 0, the expanded RAM can be accessed as
in the following example.
Expanded RAM Access (Indirect Addressing only):
MOVX@DPTR, A; DPTR contains 0A0H
DPTR points to 0A0H and data in “A” is written to address
0A0H of the expanded RAM rather than external memory.
Access to external memory higher than 2FFH using the
MOVX instruction will access external memory (0300H to
FFFFH) and will perform in the same way as the standard
8051, with P0 and P2 as data/address bus, and P3.6 and
P3.7 as write and read timing signals.
When EXTRAM = 1, MOVX @Ri and MOVX @DPTR will
be similar to the standard 8051. Using MOVX @Ri pro-
vides an 8-bit address with multiplexed data on Port 0.
Other output port pins can be used to output higher order
address bits. This provides external paging capabilities.
Using MOVX @DPTR generates a 16-bit address. This
allows external addressing up the 64K. Port 2 provides the
high-order eight address bits (DPH), and Port 0 multiplexes
the low order eight address bits (DPL) with data. Both
MOVX @Ri and MOVX @DPTR generates the necessary
read and write signals (P3.6 - WR# and P3.7 - RD#) for
external memory use. Table 3-3 shows external data mem-
ory RD#, WR# operation with EXTRAM bit.
The stack pointer (SP) can be located anywhere within the
256 bytes of internal RAM (lower 128 bytes and upper 128
bytes). The stack pointer may not be located in any part of
the expanded RAM.
TABLE
3-3: EXTERNAL DATA MEMORY RD#, WR# WITH EXTRAM BIT
MOVX @DPTR, A or MOVX A, @DPTR
MOVX @Ri, A or MOVX A, @Ri
AUXR
ADDR < 0300H
ADDR >= 0300H
ADDR = Any
EXTRAM = 0
RD# / WR# not asserted
RD# / WR# asserted
RD# / WR# not asserted1
1. Access limited to ERAM address within 0 to 0FFH; cannot access 100H to 02FFH.
EXTRAM = 1
RD# / WR# asserted
T3-3.0 1228
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SST89E554RC | 制造商:SST 制造商全称:Silicon Storage Technology, Inc 功能描述:FlashFlex51 MCU |
| SST89E554RC-25-C-NI | 制造商:SST 制造商全称:Silicon Storage Technology, Inc 功能描述:FlashFlex51 MCU |
| SST89E554RC-25-C-NJ | 制造商:SST 制造商全称:Silicon Storage Technology, Inc 功能描述:FlashFlex51 MCU |
| SST89E554RC-25-C-PI | 制造商:SST 制造商全称:Silicon Storage Technology, Inc 功能描述:FlashFlex51 MCU |
| SST89E554RC-25-C-PJ | 制造商:SST 制造商全称:Silicon Storage Technology, Inc 功能描述:FlashFlex51 MCU |
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