參數資料
型號: uPSD3251
廠商: 意法半導體
英文描述: Flash Programmable System Devices with 8032 Microcontroller Core(帶8032微控制器內核的Flash可編程系統(tǒng)設備)
中文描述: 閃存可編程系統(tǒng)設備與8032微控制器內核(帶8032微控制器內核的閃存可編程系統(tǒng)設備)
文件頁數: 23/128頁
文件大?。?/td> 1566K
代理商: UPSD3251
23/128
μPSD3251F
External RAM.
Table 10 shows a list of the Data
Transfer instructions that access external Data
Memory. Only indirect addressing can be used.
The choice is whether to use a one-byte address,
@Ri, where Ri can be either R0 or R1 of the se-
lected
register
bank,
address, @DTPR.
Note:
In all external Data RAM accesses, the Ac-
cumulator is always either the destination or
source of the data.
Lookup Tables.
Table 11 shows the two instruc-
tions that are available for reading lookup tables in
Program Memory. Since these instructions access
only Program Memory, the lookup tables can only
be read, not updated.
The mnemonic is MOVC for
move constant.
The
first MOVC instruction in Table 11 can accommo-
date a table of up to 256 entries numbered 0
through 255. The number of the desired entry is
loaded into the Accumulator, and the Data Pointer
is set up to point to the beginning of the table.
Then:
MOVC A, @A+DPTR
copies the desired table entry into the Accumula-
tor.
or
a
two-byte
The other MOVC instruction works the same way,
except the Program Counter (PC) is used as the
table base, and the table is accessed through a
subroutine. First the number of the desired en-try
is loaded into the Accumulator, and the subroutine
is called:
MOV A , ENTRY NUMBER
CALL TABLE
The subroutine
TABLE
would look like this:
TABLE: MOVC A , @A+PC
RET
The table itself immediately follows the RET (re-
turn) instruction is Program Memory. This type of
table can have up to 255 entries, numbered 1
through 255. Number 0 cannot be used, because
at the time the MOVC instruction is executed, the
PC contains the address of the RET instruction.
An entry numbered 0 would be the RET opcode it-
self.
Table 10. Data Transfer Instruction that Access External Data Memory Space
Table 11. Lookup Table READ Instruction
Address Width
Mnemonic
Operation
8 bits
MOVX A,@Ri
READ external RAM @Ri
8 bits
MOVX @Ri,A
WRITE external RAM @Ri
16 bits
MOVX A,@DPTR
READ external RAM @DPTR
16 bits
MOVX @DPTR,a
WRITE external RAM @DPTR
Mnemonic
Operation
MOVC A,@A+DPTR
READ program memory at (A+DPTR)
MOVC A,@A+PC
READ program memory at (A+PC)
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