AT94K ATMEL Corporation, AT94K Datasheet - Page 131

• Manufacturer Part Number: AT94K
• Description: 5K - 40K Gates of At40k FPGA with 8-bit Microcontroller, up to 36K Bytes of SRAM and On-chip JTAG ICE
• Manufacturer: ATMEL Corporation

Rev. 1138F–FPSLI–06/02
Figure 70. Block diagram of the 2-wire Serial Bus Interface
The CPU interfaces with the 2-wire Serial Interface via the following five I/O registers: the 2-
wire Serial Bit-rate Register (TWBR), the 2-wire Serial Control Register (TWCR), the 2-wire
Serial Status Register (TWSR), the 2-wire Serial Data Register (TWDR), and the 2-wire Serial
Address Register (TWAR, used in Slave mode).
The 2-wire Serial Bit-rate Register – TWBR
Bit
$1C ($3C)
Read/Write
Initial Value
SDA
SCL
7
TWBR7
R/W
0
OUTPUT
OUTPUT
INPUT
INPUT
6
TWBR6
R/W
0
5
TWBR5
R/W
0
TWAR
ADDRESS REGISTER
TWDR
STATUS DECODER
STATE MACHINE
SERIAL CLOCK
COMPARATOR
ARBITRATION
GENERATOR
START/STOP
DATA SHIFT
REGISTER
AND SYNC
4
TWBR4
R/W
0
STATUS
AND
AND
3
TWBR3
R/W
0
AT94K Series FPSLIC
2
TWBR2
R/W
0
TWCR
TWSR
REGISTER
REGISTER
CONTROL
CONTROL
STATUS
TIMING
AND
ACK
1
TWBR1
R/W
0
0
TWBR0
R/W
0
TWBR
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