80C554 Datasheet, PDF (12/76 Pages) NXP Semiconductors – 80C51 8-bit microcontroller . 6 clock operation 16K/512 OTP/ROM/ROMless, 7 channel 10 bit A/D, I2C, PWM, capture/compare, high I/O, 64L LQFP

Philips Semiconductors
80C51 8-bit microcontroller – 6 clock operation
16K/512 OTP/ROM/ROMless, 7 channel 10 bit A/D, I²C, PWM,
capture/compare, high I/O, 64L LQFP
Preliminary specification
80C554/83C554/87C554
FF
ERAM
256 BYTES
FF
FF
UPPER
128 BYTES
INTERNAL RAM
80
SPECIAL
FUNCTION
REGISTER
80
FFFF
EXTERNAL
DATA
MEMORY
LOWER
128 BYTES
INTERNAL RAM
00
00
00
0100
0000
SU00980
Figure 5. Internal and External Data Memory Address Space with EXTRAM = 0
Dual DPTR
The dual DPTR structure (see Figure 6) is a way by which the chip
will 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.
The DPS bit status should be saved by software when switching
between DPTR0 and DPTR1.
DPS
BIT0
AUXR1
DPH
(83H)
DPL
(82H)
DPTR1
DPTR0
Figure 6.
EXTERNAL
DATA
MEMORY
SU00745A
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 AUXR1 instruction without affecting the other 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:
INC DPTR
Increments the data pointer by 1
MOV DPTR, #data16 Loads the DPTR with a 16-bit constant
MOV A, @ A+DPTR Move code byte relative to DPTR to ACC
MOVX A, @ DPTR
Move external RAM (16-bit address) to
ACC
MOVX @ DPTR , A
Move ACC to external RAM (16-bit
address)
JMP @ A + DPTR
Jump indirect relative to DPTR
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.
2000 Nov 10
12