Philips Semiconductors Product specification
P83C557E4/P80C557E4/P89C557E4Single-chip 8-bit microcontroller
1999 Mar 02
10
MOVX @DPTR,A
MOVX A,@DPTR
MOVX A, @Ri
MOVX @Ri, A
255
255
0
255
0
0
767
(XRAMP) = 02 H
(XRAMP) = 01 H
(XRAMP) = 00 H
0
Figure 5. Indirect addressing of AUX-RAM (768 Bytes), ARD bit in PCON = 0
512
511
256
255
6.2.2.1 AUX-RAM Page Register XRAMP
The AUX-RAM Page Register is used to select one of three 256
bytes pages of the internal 768 bytes AUX-RAM for
MOVX-accesses via R0 or R1. Its reset value is (XXXXXX00).
7 6 5 4 3 2 1 0
x x x x x x XRAMP1 XRAMP0
XRAMP (FAH)
Figure 6. AUX-RAM page register.
x: undefined during read, a write operation must write “0” to these locations
Table 3. Description of XRAMP Bits
BIT SYMBOL FUNCTION
XRAMP.2–7 XRAMPx reserved for future use
XRAMP.1 XRAMP1 AUX-RAM page select bit 1
XRAMP.0 XRAMP0 AUX-RAM page select bit 0
Table 4. Memory Locations for All Possible MOVX Accesses
ARD
1
XRAMP1 XRAMP0 MOVX @Ri,A and MOVX A,@Ri instructions access:
0 0 0 AUX-RAM locations 0 .. 255 (reset condition)
0 0 1 AUX-RAM locations 256 .. 511
0 1 0 AUX-RAM locations 512 .. 767
0 1 1 no valid memory access; reserved for future use
1 X X External RAM locations 0 .. 255
MOVX @DPTR,A and MOVX A,@DPTR instructions access:
0 X X AUX-RAM locations 0 .. 767 (reset condition)
External RAM locations 768 .. 65535
1 X X External RAM locations 0 .. 65535
NOTE:
1. ARD (AUX-RAM Disable) is a bit in the Special Function Register PCON
