P83CE559 Datasheet, PDF (11/72 Pages) NXP Semiconductors – Single-chip 8-bit microcontroller

Philips Semiconductors
Single-chip 8-bit microcontroller
Preliminary specification
P83CE559/P80CE559
6.2.2.1 AUX–RAM Page Register XRAMP
The AUX–RAM Page Register is used to select one of five 256
bytes pages of the internal 1280 bytes AUX–RAM for
MOVX–accesses via R0 or R1. Its reset value is (XXXXX000).
XRAMP (FAH)
7
6
5
4
3
x
x
x
x
x
x: undefined during read, a write operation must write “0” to these locations
Figure 6. AUX–RAM page register.
2
XRAMP2
1
XRAMP1
0
XRAMP0
Table 3. Description of XRAMP bits
BIT
SYMBOL
FUNCTION
XRAMP.3–7
XRAMP.2
XRAMP.1
XRAMP.0
XRAMPx
XRAMP2
XRAMP1
XRAMP0
reserved for future use
AUX–RAM page select bit 2
AUX–RAM page select bit 1
AUX–RAM page select bit 0
Table 4. Memory locations for all possible MOVX–accesses
ARD¹
XRAMP2 XRAMP1 XRAMP0 MOVX @Ri,A and MOVX A,@Ri instructions access:
0
0
0
0
AUX–RAM locations 0 .. 255 (reset condition)
0
0
0
1
AUX–RAM locations 256 .. 511
0
0
1
0
AUX–RAM locations 512 .. 767
0
0
1
1
AUX–RAM locations 768 ... 1023
0
1
0
0
AUX–RAM locations 1024 .. 1279
0
1
0
1
no valid memory access; reserved for future use
0
1
1
X
no valid memory access; reserved for future use
1
X
X
X
External RAM locations 0 .. 255
MOVX @DPTR,A and MOVX A,@DPTR instructions access:
0
X
X
X
AUX–RAM locations 0 .. 1279 (reset condition)
External RAM locations 1280 .. 65535
1
X
X
X
External RAM locations 0 .. 65535
NOTE:
1. ARD (AUX–RAM Disable) is a bit in the Special Function Register PCON
1996 Aug 06
11