
59
ATmega16(L)
2466B–09/01
an open drain driver with slew-rate limitation. When this pin is used by the 2-wire Serial
Interface, the pull-up can still be controlled by the PORTC1 bit.
• SCL - Port C, Bit 0
SCL, 2-wire Serial Interface Clock: When the TWEN bit in TWCR is set (one) to enable
the 2-wire Serial Interface, pin PC0 is disconnected from the port and becomes the
Serial Clock I/O pin for the 2-wire Serial Interface. In this mode, there is a spike filter on
the pin to suppress spikes shorter than 50 ns on the input signal, and the pin is driven by
an open drain driver with slew-rate limitation. When this pin is used by the 2-wire Serial
Interface, the pull-up can still be controlled by the PORTC0 bit.
Table 29 and Table 30 relate the alternate functions of Port C to the overriding signals
shown in Figure 26 on page 52.
Note: 1. When enabled, the Two-Wire Serial Interface enables slew-rate controls on the output
pins PC0 and PC1. This is not shown in the figure. In addition, spike filters are con-
nected between the AIO outputs shown in the port figure and the digital logic of the
TWI module.
Table 29. Overriding Signals for Alternate Functions in PC7..PC4
Signal
Name PC7/TOSC2 PC6/TOSC1 PC5/TDI PC4/TDO
PUOE AS2 AS2 JTAGEN JTAGEN
PUOV 0 0 1 0
DDOE AS2 AS2 JTAGEN JTAGEN
DDOV 0 0 0 SHIFT_IR + SHIFT_DR
PVOE 0 0 0 JTAGEN
PVOV 0 0 0 TDO
DIEOE AS2 AS2 JTAGEN JTAGEN
DIEOV 0 0 0 0
DI ––––
AIO T/C2 OSC OUTPUT T/C2 OSC INPUT TDI –
Table 30. Overriding Signals for Alternate Functions in PC3..PC0
(1)
Signal
Name PC3/TMS PC2/TCK PC1/SDA PC0/SCL
PUOE JTAGEN JTAGEN TWEN TWEN
PUOV 1 1 PORTC1 • PUD
PORTC0 • PUD
DDOE JTAGEN JTAGEN TWEN TWEN
DDOV 0 0 SDA_OUT SCL_OUT
PVOE 0 0 TWEN TWEN
PVOV 0 0 0 0
DIEOE JTAGEN JTAGEN 0 0
DIEOV 0 0 0 0
DI ––– –
AIO TMS TCK SDA INPUT SCL INPUT
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