
160
8008H–AVR–04/11
ATtiny48/88
Bit 0 – TWGCE: TWI General Call Recognition Enable Bit
If set, this bit enables the recognition of a General Call given over the 2-wire Serial Bus.
15.11.6
TWAMR – TWI (Slave) Address Mask Register
Bits 7:1 – TWAM: TWI Address Mask
The TWAMR can be loaded with a 7-bit Salve Address mask. Each of the bits in TWAMR can
mask (disable) the corresponding address bits in the TWI Address Register (TWAR). If the mask
bit is set to one then the address match logic ignores the compare between the incoming
address bit and the corresponding bit in TWAR.
Figure 15-22 shown the address match logic in
detail.
Figure 15-22. TWI Address Match Logic, Block Diagram
Bit 0 – Res: Reserved Bit
This bit is reserved and will always read zero.
15.11.7
TWHSR – TWI High Speed Register
Bits 7:1 – Res: Reserved Bits
These bits are reserved and will always read zero.
Bit 0 – TWHS: TWI High Speed Enable
TWI High Speed mode is enabled by writing this bit to one. In this mode the undivided system
The TWI High Speed mode requires that the high-speed clock, clk
TWIHS, is exactly two times
higher than the I/O clock frequency, clk
I/O. This means the user must make sure the I/O clock
frequency clk
I/O is scaled down by a factor of 2. For example, if the internal 8 MHz oscillator has
been selected as source clock, the user must set the prescaler to scale the system clock (and,
hence, the I/O clock) down to 4 MHz. For more information about clock systems, see
“ClockBit
7
654
32
10
TWAM[6:0]
–
TWAMR
Read/Write
R/W
R
Initial Value
0
Address
Match
Address Bit Comparator 0
Address Bit Comparator 6..1
TWAR0
TWAMR0
Address
Bit 0
Bit
7
654
32
10
–
–––
––
–
TWHS
TWHSR
Read/Write
RR
R
R/W
Initial Value
0