Rainbow Electronics ATmega128L - Manual (Page 68)

68
ATmega128(L)
2467B–09/01
• 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 61 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 28 and Table 29 relates the alternate functions of Port A to the overriding signals
shown in
Figure 32 on page 66.
Note: 1. ADA is short for ADdress Active and represents the time when address is output. See
“External Memory Interface” on page 24 for details.
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. Overriding Signals for Alternate Functions in PA7..PA4
Signal
Name
PA7/AD7 PA6/AD6 PA5/AD5 PA4/AD4
PUOE SRE SRE SRE SRE
PUOV ~(WR | ADA (1) ) •
PORTA7 • PUD
~(WR | ADA) •
PORTA6 • PUD ~(WR | ADA) •
PORTA5 • PUD ~(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 – – – –