ATMEGA128 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'ATMEGA128' PDF : 395 Pages View PDF
Special Function IO Register –
SFIOR
Bit
7
6
5
4
3
2
1
0
TSM
–
–
–
ACME
PUD
PSR0 PSR321 SFIOR
Read/Write
R/W
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
• Bit 2 – PUD: Pull-up disable
When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn
and PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01).
See “Configuring the Pin” on page 66 for more details about this feature.
Alternate Functions of Port A The Port A has an alternate function as the address low byte and data lines for the
External Memory Interface.
Table 27. Port A Pins Alternate Functions
Port Pin Alternate Function
PA7
AD7 (External memory interface address and data bit 7)
PA6
AD6 (External memory interface address and data bit 6)
PA5
AD5 (External memory interface address and data bit 5)
PA4
AD4 (External memory interface address and data bit 4)
PA3
AD3 (External memory interface address and data bit 3)
PA2
AD2 (External memory interface address and data bit 2)
PA1
AD1 (External memory interface address and data bit 1)
PA0
AD0 (External memory interface address and data bit 0)
Table 28 and Table 29 relates the alternate functions of Port A to the overriding signals
shown in Figure 33 on page 70.
Table 28. Overriding Signals for Alternate Functions in PA7..PA4
Signal
Name PA7/AD7
PA6/AD6
PA5/AD5
PA4/AD4
PUOE
PUOV
SRE
~(WR | ADA(1)) •
PORTA7 • PUD
SRE
~(WR | ADA) •
PORTA6 • PUD
SRE
~(WR | ADA) •
PORTA5 • PUD
SRE
~(WR | ADA) •
PORTA4 • PUD
DDOE SRE
SRE
SRE
SRE
DDOV WR | ADA
WR | ADA
WR | ADA
WR | ADA
PVOE SRE
SRE
SRE
SRE
PVOV A7 • ADA | D7
OUTPUT • WR
A6 • ADA | D6
OUTPUT • WR
A5 • ADA | D5
OUTPUT • WR
A4 • ADA | D4
OUTPUT • WR
DIEOE 0
0
0
0
DIEOV 0
0
0
0
DI
D7 INPUT
D6 INPUT
D5 INPUT
D4 INPUT
AIO
–
–
–
–
Note: 1. ADA is short for ADdress Active and represents the time when address is output. See
“External Memory Interface” on page 26 for details.
72 ATmega128
2467O–AVR–10/06
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