Rainbow Electronics ATtiny26L - Manual (Page 96)

96
ATtiny26(L)
1477B–AVR–04/02
The following subsections shortly describes the alternate functions for each port, and
relates the overriding signals to the alternate function. Refer to the alternate function
description for further details.
MCU Control Register –
MCUCR The MCU Control Register contains control bits for general MCU functions.
• Bit 6 – PUD: Pull-up Disable
When this bit is set (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 91 for more details about this feature.
Table 40. Generic Description of Overriding Signals for Alternate Functions
Signal Name Full Name Description
PUOE Pull-up Override
Enable If this signal is set, the pull-up enable is controlled by
the PUOV signal. If this signal is cleared, the pull-up is
enabled when {DDxn, PORTxn, PUD} = 0b010.
PUOV Pull-up Override
Value If PUOE is set, the pull-up is enabled/disabled when
PUOV is set/cleared, regardless of the setting of the
DDxn, PORTxn, and PUD Register bits.
DDOE Data Direction
Override Enable If this signal is set, the Output Driver Enable is
controlled by the DDOV signal. If this signal is cleared,
the Output driver is enabled by the DDxn Register bit.
DDOV Data Direction
Override Value If DDOE is set, the Output Driver is enabled/disabled
when DDOV is set/cleared, regardless of the setting of
the DDxn Register bit.
PVOE Port Value
Override Enable If this signal is set and the Output Driver is enabled,
the port value is controlled by the PVOV signal. If
PVOE is cleared, and the Output Driver is enabled, the
port Value is controlled by the PORTxn Register bit.
PVOV Port Value
Override Value If PVOE is set, the port value is set to PVOV,
regardless of the setting of the PORTxn Register bit.
DIEOE Digital Input Enable
Override Enable If this bit is set, the Digital Input Enable is controlled by
the DIEOV signal. If this signal is cleared, the Digital
Input Enable is determined by MCU-state (Normal
mode, sleep modes).
DIEOV Digital Input Enable
Override Value If DIEOE is set, the Digital Input is enabled/disabled
when DIEOV is set/cleared, regardless of the MCU
state (Normal mode, sleep modes).
DI Digital Input This is the Digital Input to alternate functions. In the
figure, the signal is connected to the output of the
schmitt trigger but before the synchronizer. Unless the
Digital Input is used as a clock source, the module with
the alternate function will use its own synchronizer.
AIO Analog Input/output This is the Analog Input/Output to/from alternate
functions. The signal is connected directly to the pad,
and can be used bidirectionally.
Bit 7 6 5 4 3 2 1 0
$35 ($55) – PUD SE SM1 SM0 – ISC01 ISC00 MCUCR
Read/Write R R/W R/W R/W R/W R R/W R/W
Initial Value 0 0 0 0 0 0 0 0