T89C51RD2-3CBC-L ATMEL [ATMEL Corporation], T89C51RD2-3CBC-L Datasheet - Page 46

• Manufacturer Part Number: T89C51RD2-3CBC-L
• Description: 0 to 40MHz Flash Programmable 8-bit Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

6.12. Reduced EMI Mode
The ALE signal is used to demultiplex address and data buses on port 0 when used with external program or data
memory. Nevertheless, during internal code execution, ALE signal is still generated. In order to reduce EMI, ALE
signal can be disabled by setting AO bit.
The AO bit is located in AUXR register at bit location 0. As soon as AO is set, ALE is no longer output but
remains active during MOVX and MOVC instructions and external fetches. During ALE disabling, ALE pin is
weakly pulled high.
AUXR - Auxiliary Register (8Eh)
Reset Value = XX0X 1000b
Not bit addressable
Rev. F - 15 February, 2001
Number
Bit
7
6
5
4
3
2
1
0
7
-
Mnemonic
EXTRAM
XRS1
XRS0
Bit
M0
AO
-
-
-
6
-
Reserved
Reserved
M0 bit: Pulse length in clock period
Reserved
XRS1 bit
XRS0 bit
EXTRAM bit
ALE Output bit
Stretch MOVX control: the RD/ and the WR/ pulse length is increased according to the value of M0. see table 6
The value read from this bit is indeterminate. Do not set this bit.
The value read from this bit is indeterminate. Do not set this bit.
The value read from this bit is indeterminate. Do not set this bit.
XRAM size: Accessible size of the XRAM. See Table 6.
XRAM size: Accessible size of the XRAM. Table 6.
See Table 6.
Clear to restore ALE operation during internal fetches.
Set to disable ALE operation during internal fetches.
M0
5
Table 24. AUXR Register
4
-
XRS1
3
Description
XRS0
2
T89C51RD2
EXTRAM
1
AO
0
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