AT89LP51 Atmel Corporation, AT89LP51 Datasheet - Page 28

• Manufacturer Part Number: AT89LP51
• Manufacturer: Atmel Corporation

Specifications of AT89LP51

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 36
• Uart: 1
• Sram (kbytes): 0.25
• Eeprom (bytes): 256
• Self Program Memory: IAP
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 3
• Isp: SPI
• Watchdog: Yes

Table 5-3.
28
Symbol
DPU1
DPU0
DPD1
DPD0
SIGEN
DPS
AUXR1 = A2H
Not Bit Addressable
Bit
AT89LP51/52
Function
Data Pointer 1 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR1 will also update
DPTR1 based on DPD1. If DPD1 = 0 the operation is post-increment and if DPD1 = 1 the operation is post-decrement.
When DPU1 = 0, DPTR1 is not updated.
Data Pointer 0 Update. When set, MOVX @DPTR and MOVC @DPTR instructions that use DPTR0 will also update
DPTR0 based on DPD0. If DPD0 = 0 the operation is post-increment and if DPD0 = 1 the operation is post-decrement.
When DPU0 = 0, DPTR0 is not updated.
Data Pointer 1 Decrement. When set, INC DPTR instructions targeted to DPTR1 will decrement DPTR1. When cleared,
INC DPTR instructions will increment DPTR1. DPD1 also determines the direction of auto-update for DPTR1 when
DPU1 = 1.
Data Pointer 0 Decrement. When set, INC DPTR instructions targeted to DPTR0 will decrement DPTR0. When cleared,
INC DPTR instructions will increment DPTR0. DPD0 also determines the direction of auto-update for DPTR0 when
DPU0 = 1.
Signature Enable. When SIGEN = 1 all MOVC @DPTR instructions and all IAP accesses will target the signature array
memory. When SIGEN = 0, all MOVC and IAP accesses target CODE memory.
Data Pointer Select. DPS selects the active data pointer for instructions that reference DPTR. When DPS = 0, DPTR will
target DPTR0 and /DPTR will target DPTR1. When DPS = 1, DPTR will target DPTR1 and /DPTR will target DPTR0.
AUXR1
DPU1
7
– Data Pointer Configuration Register
Table 5-2.
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
5-4. These bits can be used to make block copy routines more efficient.
Table 5-4.
DPU0
DPD1
DPD1
0
0
1
1
6
0
0
1
1
DPD0
DPD0
Data Pointer Decrement Behavior
Data Pointer Auto-Update
0
1
0
1
0
1
0
1
DPD1
5
DEC DPTR0
DEC DPTR0
INC DPTR0
INC DPTR0
INC DPTR
DPTR0++
DPTR0++
DPTR0--
DPTR0--
DPTR
DPD0
Update Operation for MOVX and MOVC (DPU1 = 1 & DPU0 = 1)
4
Equivalent Operation for INC DPTR and INC /DPTR
DPS = 0
DPS = 0
SIGEN
DEC DPTR1
DEC DPTR1
INC DPTR1
INC DPTR1
INC /DPTR
3
DPTR1++
DPTR1++
DPTR1--
DPTR1--
/DPTR
0
2
DEC DPTR1
DEC DPTR1
INC DPTR1
INC DPTR1
INC DPTR
DPTR1++
DPTR1++
DPTR1--
DPTR1--
DPTR
Reset Value = 0000 00X0B
–
1
DPS = 1
DPS = 1
DEC DPTR0
DEC DPTR0
INC DPTR0
INC DPTR0
3709D–MICRO–12/11
INC /DPTR
DPTR0++
DPTR0++
DPTR0--
DPTR0--
DPS
/DPTR
0
Table