AT89LP51RD2 Atmel Corporation, AT89LP51RD2 Datasheet - Page 38

• Manufacturer Part Number: AT89LP51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 42
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Adc Channels: 7
• Adc Resolution (bits): 10
• Adc Speed (ksps): 153.8
• Sram (kbytes): 2.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

5.4.1
38
AT89LP51RD2/ED2/ID2 Preliminary
Data Pointer Update
A summary of data pointer instructions with fast context switching is listed
Table 5-3.
The Dual Data Pointers on the AT89LP51RD2/ED2/ID2 include two features that control how
the data pointers are updated. The data pointer decrement bits, DPD1 and DPD0 in AUXR1,
configure the INC DPTR instruction to act as DEC DPTR. The resulting operation will depend on
DPS as shown in
and MOVX.
Table 5-4.
The data pointer update bits, DPU1 and DPU0, allow MOVX @DPTR and MOVC @DPTR
instructions to update the selected data pointer automatically in a post-increment or post-decre-
ment fashion. The direction of update depends on the DPD1 and DPD0 bits as shown in
5-5. These bits can be used to make block copy routines more efficient. Note that DPCF should
be cleared to zero, disabling these modes, before any calls are made to the Flash API.Care
must also be taken when interrupt routines use data pointers to ensure that correct operation is
saved/restored correctly.
Instruction
JMP @A+DPTR
MOV DPTR, #data16
MOV /DPTR, #data16
INC DPTR
INC /DPTR
MOVC A,@A+DPTR
MOVC A,@A+/DPTR
MOVX A,@DPTR
MOVX A,@/DPTR
MOVX @DPTR, A
MOVX @/DPTR, A
DPD1
0
0
1
1
DPD0
Data Pointer Instructions
Data Pointer Decrement Behavior
0
1
0
1
Table
5-4. These bits also control the direction of auto-updates during MOVC
DEC DPTR0
DEC DPTR0
INC DPTR0
INC DPTR0
INC DPTR
Equivalent Operation for INC DPTR and INC /DPTR
DPS = 0
DEC DPTR1
DEC DPTR1
INC DPTR1
INC DPTR1
INC /DPTR
DPS = 0
JMP @A+DPTR0
MOV DPTR0, #data16
MOV DPTR1, #data16
INC DPTR0
INC DPTR1
MOVC A,@A+DPTR0
MOVC A,@A+DPTR1
MOVX A,@DPTR0
MOVX A,@DPTR1
MOVX @DPTR0, A
MOVX @DPTR1, A
DEC DPTR1
DEC DPTR1
INC DPTR1
INC DPTR1
INC DPTR
Operation
DPS = 1
DPS = 1
JMP @A+DPTR1
MOV DPTR1, #data16
MOV DPTR0, #data16
INC DPTR1
INC DPTR0
MOVC A,@A+DPTR1
MOVC A,@A+DPTR0
MOVX A,@DPTR1
MOVX A,@DPTR0
MOVX @DPTR1, A
MOVX @DPTR0, A
inTable
DEC DPTR0
DEC DPTR0
INC DPTR0
INC DPTR0
INC /DPTR
3714A–MICRO–7/11
5-3.
Table