AT89S51-24SC ATMEL Corporation, AT89S51-24SC Datasheet - Page 7

• Manufacturer Part Number: AT89S51-24SC
• Description: 8-bit Microcontroller with 4K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

2487B–MICRO–12/03
User software should not write 1s to these unlisted locations, since they may be used in future
products to invoke new features. In that case, the reset or inactive values of the new bits will
always be 0.
Interrupt Registers: The individual interrupt enable bits are in the IE register. Two priorities
can be set for each of the five interrupt sources in the IP register.
Table 2. AUXR: Auxiliary Register
Dual Data Pointer Registers: To facilitate accessing both internal and external data memory,
two banks of 16-bit Data Pointer Registers are provided: DP0 at SFR address locations 82H-
83H and DP1 at 84H-85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1.
The user should ALWAYS initialize the DPS bit to the appropriate value before accessing the
respective Data Pointer Register.
AUXR
–
DISALE
DISRTO
WDIDLE
WDIDLE
0
1
Bit
Not Bit Addressable
Reserved for future expansion
Disable/Enable ALE
DISALE
Operating Mode
0
1
Disable/Enable Reset-out
DISRTO
0
1
Disable/Enable WDT in IDLE mode
–
7
WDT continues to count in IDLE mode
WDT halts counting in IDLE mode
Address = 8EH
–
6
ALE is emitted at a constant rate of 1/6 the oscillator frequency
ALE is active only during a MOVX or MOVC instruction
Reset pin is driven High after WDT times out
Reset pin is input only
–
5
WDIDLE
4
DISRTO
3
–
2
Reset Value = XXX00XX0B
–
1
DISALE
AT89S51
0
7