8XC51_8XC52 NXP Semiconductors, 8XC51_8XC52 Datasheet - Page 20

• Manufacturer Part Number: 8XC51_8XC52
• Description: The Philips 80C51/87C51/80C52/87C52 is a high-performancestatic 80C51 design fabricated with Philips high-density CMOStechnology with operation from 2
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Reduced EMI
All port pins of the 8xC51 and 8xC52 have slew rate controlled
outputs. This is to limit noise generated by quickly switching output
signals. The slew rate is factory set to approximately 10 ns rise and
fall times.
Reduced EMI Mode
The AO bit (AUXR.0) in the AUXR register when set disables the
ALE output.
AUXR (8EH)
AUXR.0
Dual DPTR
The dual DPTR structure (see Figure 13) enables a way to specify
the address of an external data memory location. There are two
16-bit DPTR registers that address the external memory, and a
single bit called DPS = AUXR1/bit0 that allows the program code to
switch between them.
AUXR1 (A2H)
Where:
The DPS bit status should be saved by software when switching
between DPTR0 and DPTR1.
2000 Aug 07
New Register Name: AUXR1#
SFR Address: A2H
Reset Value: xxx000x0B
DPS = AUXR1/bit0 = Switches between DPTR0 and DPTR1.
80C51 8-bit microcontroller family
4 K/8 K OTP/ROM low voltage (2.7 V–5.5 V),
low power, high speed (33 MHz), 128/256 B RAM
7
–
7
–
6
–
Select Reg
6
–
DPTR0
DPTR1
AO
5
–
5
–
4
–
LPEP
4
Turns off ALE output.
WUPD
3
–
3
2
–
2
0
DPS
0
1
1
–
1
–
AO
DPS
0
0
20
Note that bit 2 is not writable and is always read as a zero. This
allows the DPS bit to be quickly toggled simply by executing an INC
DPTR instruction without affecting the WOPD or LPEP bits.
DPTR Instructions
The instructions that refer to DPTR refer to the data pointer that is
currently selected using the AUXR1/bit 0 register. The six
instructions that use the DPTR are as follows:
The data pointer can be accessed on a byte-by-byte basis by
specifying the low or high byte in an instruction which accesses the
SFRs. See application note AN458 for more details.
INC DPTR
MOV DPTR, #data16
MOV A, @ A+DPTR
MOVX A, @ DPTR
MOVX @ DPTR , A
JMP @ A + DPTR
AUXR1
DPS
BIT0
80C51/87C51/80C52/87C52
(83H)
DPH
Increments the data pointer by 1
Loads the DPTR with a 16-bit constant
Move code byte relative to DPTR to ACC
Move external RAM (16-bit address) to
ACC
Move ACC to external RAM (16-bit
address)
Jump indirect relative to DPTR
Figure 13.
(82H)
DPL
DPTR1
DPTR0
Product specification
EXTERNAL
MEMORY
DATA
SU00745A