atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 180

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

16.6
16.6.1
16.6.2
16.6.3
16.6.4
180
CAN Timer
ATmega32/64/M1/C1
Prescaler
16-bit Timer
Time Triggering
Stamping Message
The data index (INDX) is the address pointer to the required data byte. The data byte can be
read or write. The data index is automatically incremented after every access if the AINC* bit is
reset. A roll-over is implemented, after data index=7 it is data index=0.
The first byte of a CAN frame is stored at the data index=0, the second one at the data index=1,
...
A programmable 16-bit timer is used for message stamping and time trigger communication
(TTC).
Figure 16-11. CAN Timer Block Diagram
An 8-bit prescaler is initialized by CANTCON register. It receives the clk
8. It provides clk
T
This timer starts counting from 0x0000 when the CAN controller is enabled (ENFG bit). When
the timer rolls over from 0xFFFF to 0x0000, an interrupt is generated (OVRTIM).
Two synchronization modes are implemented for TTC (TTC bit):
In TTC mode, a frame is sent once, even if an error occurs.
The capture of the timer value is done in the MOb which receives or sends the frame. All man-
aged MOb are stamped, the stamping of a received (sent) frame occurs on RxOk (TXOK).
clk
CANTIM
– synchronization on Start of Frame (SYNCTTC=0),
– synchronization on End of Frame (SYNCTTC=1).
RXOK[i]
TXOK[i]
clk
IO
=
T
OVRTIM
clk
CANTIM
IO
x 8 x (CANTCON [7:0] + 1)
8
frequency to the CAN Timer if the CAN controller is enabled.
CANSTM[i]
overrun
CANTCON
CANTIM
clk
CANTIM
ENFG
CANTTC
IO
TTC
frequency divided by
SYNCTTC
7647A–AVR–02/08
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