
214
XMEGA A [MANUAL]
8077I–AVR–11/2012
19.8
Register Description – TWI
19.8.1 CTRL – Common Control register
Bit 7:2 – Reserved
These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to zero
when this register is written.
Bit 1 – SDAHOLD: SDA Hold Time Enable.
Setting these bits to one enables an internal hold time on SDA with respect to the negative edge of SCL.
Table 19-1. SDA hold time.
Bit 0 – EDIEN: External Driver Interface Enable
Setting this bit enables the use of the external driver interface, and clearing this bit enables normal two-wire mode. See
Table 19-2. External driver interface enable.
19.9
Register Description – TWI Master
19.9.1 CTRLA
– Control register A
Bit 7:6
– INTLVL[1:0]: Interrupt Level
Bit 5
– RIEN: Read Interrupt Enable
Setting the read interrupt enable (RIEN) bit enables the read interrupt when the read interrupt flag (RIF) in the STATUS
register is set. In addition the INTLVL bits must be nonzero for TWI master interrupts to be generated.
Bit
76543210
+0x00
–
SDAHOLD
EDIEN
Read/Write
RRRRRR
R/W
Initial Value
00000000
SDAHOLD
Group configuration
Description
0
OFF
SDA hold time off
1
50NS
Typical 50ns hold time
EDIEN
Mode
Comment
0
Normal TWI
Two-pin interface, slew rate control, and input filter.
1
External driver interface
Four-pin interface, standard I/O, no slew rate control, and no input filter.
Bit
76543210
+0x00
INTLVL[1:0]
RIEN
WIEN
ENABLE
–
Read/Write
R/W
R
Initial Value
00000000