AT87C54X2-3CSUL View Datasheet(PDF) - Atmel Corporation
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Description
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AT87C54X2-3CSUL Datasheet PDF : 62 Pages
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AT/TS8xC54/8X2
15. Reduced EMI Mode
The ALE signal is used to demultiplex address and data buses on port 0 when used with exter-
nal 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.
Table 15-1. AUXR Register
AUXR - Auxiliary Register (8Eh)
7
6
5
4
3
-
-
-
-
-
2
1
0
-
RESERVED
AO
Bit
Number
7
6
5
4
3
2
1
0
Bit
Mnemonic
-
-
-
-
-
-
-
AO
Description
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
Reserved
The value read from this bit is indeterminate. Do not set this bit.
ALE Output bit
Clear to restore ALE operation during internal fetches.
Set to disable ALE operation during internal fetches.
Reset Value = XXXX XXX0b
Not bit addressable
35
4431E–8051–04/06
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