t89c51rd2-slscl ATMEL Corporation, t89c51rd2-slscl Datasheet - Page 17

• Manufacturer Part Number: t89c51rd2-slscl
• Description: 0 To 40 Mhz Flash Programmable 8-bit Microcontroller
• Manufacturer: ATMEL Corporation

4243G–8051–05/03
Table 7. Auxiliary Register (08EH)
1.
Address 08EH
EXTRAM
Symbol
XRS0
XRS1
AUXR
AO
M0
-
User software should not write 1s to reserved bits. These bits may be used in future 8051
family products to invoke new features. In that case, the reset or inactive value of the
new bit will be 0, and its active value will be 1. The value read from a reserved bit is
indeterminate.
Function
Not implemented, reserved for future use.
Disable/Enable ALE
Internal/External RAM (00H-FFH) access using MOVX @ Ri/ @ DPTR
XRAM size: Accessible size of the XRAM
Stretch MOVX control: the RD/ and the WR/ pulse length is increased according to the
value of M0
EXTRAM
XRS1:0
Reset value
AO
0 0
0 1
1 0
1 1
M0
0
1
0
1
0
1
Operating Mode
ALE is emitted at a constant rate of 1/6 the oscillator frequency (or 1/3 if X2
mode is used)
ALE is active only during a MOVX or MOVC instruction
Operating Mode
Internal XRAM access using MOVX @ Ri/ @ DPTR
External data memory access
XRAM size
256 bytes
512 bytes
768 bytes (default)
1024 bytes
Pulse length in clock period
6
30
X
-
X
-
M0
0
(1)
X
-
XRS1
1
T89C51RD2
XRS0
0
EXTRA
M
0
AO
0
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