atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 175

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

16.4.3
7647A–AVR–02/08
Notes: 1. Phase error < 0
Baud Rate
5. Synchronization Segment: SYNS
2. Phase error > 0
3. Phase error > 0
4. Phase error < 0
Tsyns=1
x
Tscl (
The total number of TQ in a bit time has to be programmed at least from 8 to 25.
Figure 16-7. Sample and Transmission Point
Figure 16-8. General Structure of a Bit Period
With no baud rate prescaler (BRP[5..0]=0) the sampling point comes one time quantum too
early. This leads to a fail according the ISO16845 Test plan. It is necessary to lengthen the
Phase Segment 1 by one time quantum and to shorten the Phase Segment 2 by one time quan-
tum to compensate.
The baud rate selection is made by T
CLK
1. Tsyns = 1 x Tscl = (BRP[5..0]+ 1)/clk
2. Tprs = (1 to 8) x Tscl = (PRS[2..0]+ 1) x Tscl
3. Tphs1 = (1 to 8) x Tscl = (PHS1[2..0]+ 1) x Tscl
4. Tphs2 = (1 to 8) x Tscl = (PHS2[2..0]
fixed
F
Data
CAN
)
IO
CLK
IO
Tbit
Tsyns(5)
(1)
= Tsyns + Tprs + Tphs1 + Tphs2
1
Prescaler BRP
/
CLK
IO
Tscl (TQ)
Tprs
bit
Time Quantum
calculation:
Fcan (Tscl)
Bit Rate Prescaler
IO
one nominal bit
(2)
+ 1) x Tscl
(= 1TQ)
Tbit
Tphs1+Tsjw
Tphs1
PHS1 (3-bit length)
PHS2 (3-bit length)
PRS (3-bit length)
SJW (2-bit length)
ATmega32/64/M1/C1
Bit Timing
or
(
1
)
(
3
Sample
)
Point
Tphs2+Tsjw
Tphs2
or
Transmission
(
2
Transmission
)
(
Sample
4
)
Point
Point
Point
175