AT32UC3A464S Atmel Corporation, AT32UC3A464S Datasheet - Page 478

• Manufacturer Part Number: AT32UC3A464S
• Manufacturer: Atmel Corporation

Specifications of AT32UC3A464S

• Flash (kbytes): 64 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 66 MHz
• Cpu: 32-bit AVR
• Hardware Qtouch Acquisition: No
• Usb Transceiver: 1
• Usb Speed: Hi-Speed
• Usb Interface: Device + OTG
• Spi: 6
• Twi (i2c): 2
• Uart: 4
• Ssc: 1
• Sd / Emmc: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: AES
• Sram (kbytes): 128
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: Yes
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 3.0 to 3.6
• Operating Voltage (vcc): 3.0 to 3.6
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 6
• Output Compare Channels: 6
• Input Capture Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

23.8.2.1
32072G–11/2011
Clock Generation
The Clock Waveform Generator Register (CWGR) is used to control the waveform of the TWCK
clock. CWGR must be written so that the desired TWI bus timings are generated. CWGR
describes bus timings as a function of cycles of a prescaled clock. The clock prescaling can be
selected through the Clock Prescaler field in CWGR (CWGR.EXP).
CWGR has the following fields:
LOW: Prescaled clock cycles in clock low count. Used to time T
HIGH: Prescaled clock cycles in clock high count. Used to time T
STASTO: Prescaled clock cycles in clock high count. Used to time T
DATA: Prescaled clock cycles for data setup and hold count. Used to time T
EXP: Specifies the clock prescaler setting.
Note that the total clock low time generated is the sum of T
Any slave or other bus master taking part in the transfer may extend the TWCK low period at any
time.
The TWIM hardware monitors the state of the TWCK line as required by the I²C specification.
The clock generation counters are started when a high/low level is detected on the TWCK line,
not when the TWIM hardware releases/drives the TWCK line. This means that the CWGR set-
tings alone do not determine the TWCK frequency. The CWGR settings determine the clock low
time and the clock high time, but the TWCK rise and fall times are determined by the external cir-
cuitry (capacitive load, etc.).
Figure 23-5. Bus Timing Diagram
S
t
t LOW
HD:STA
t
SU:DAT
t HIGH
t
HD:DAT
f
PRESCALER
t LOW
=
f
------------------------- -
2
CLK_TWIM
(
t
t
EXP
SU:DAT
SU:STA
+
1
)
HD_DAT
Sr
LOW
HIGH
+ T
and T
HD_STA
.
SU_DAT
BUF
, T
HD_DAT
+ T
.
t
SU_STA
SU:STO
LOW
, T
.
, T
SU_DAT
SU_STO
P
.
478
.