AT91SAM7A1-AU Atmel, AT91SAM7A1-AU Datasheet - Page 276

• Manufacturer Part Number: AT91SAM7A1-AU
• Description: IC ARM7 MCU 32BIT ROMLESS144LQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91SAM7A1-AU

• Core Processor: ARM7
• Core Size: 16/32-Bit
• Speed: 40MHz
• Connectivity: CAN, EBI/EMI, SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 49
• Program Memory Type: ROMless
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 144-LQFP
• For Use With: AT91SAM7A1-EK - BOARD EVAL FOR AT91SAM7A1
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

Figure 25-5. Identifier Format from CAN_IRx Register to CAN Frame
276
CAN Frame
AT91SAM7A1
RTR
31
30
RB[1:0]
SOF
29
11-bit Identifier (Base ID)
28
27
In extended format, the identifier has to be written to the CAN_IRx register in a specific format:
CAN_IRx = ( (id & 0x1FFC0000) >> 18 ) | ( (id & 0x3FFFF) << 11 )
where (id & 0x1FFC0000) is the 11-bit base ID and (id & 0x3FFFF) is the 18-bit extended ID.
Figure 25-5
network.
Table 25-2
Table 25-2.
In an extended frame, the base ID is transmitted first, followed by the IDE bit and the SRR bit.
The extended ID is transmitted after the SRR bit.
The SRR bit (Substitute Remote Request) is a recessive bit. It is transmitted in Extended
Frames at the position of the RTR bit in standard frames and so substitutes the RTR bit in the
standard frame.
Therefore, collisions of a standard frame and an extended frame, the base ID (see Extended
Identifier below) of which is the same as the standard frame’s identifier, are resolved in such a
way that the standard frame prevails the extended frame.
Frame Type
Data frame
Remote frame
• RTR Bit (Standard and Extended Formats)
• SRR Bit (Extended Format)
• IDE Bit (Extended Format)
26
– Base ID: the base ID consists of 11 bits. It is transmitted in the order from ID10 to
– Extended ID: the Extended ID consists of 18 bits. It is transmitted in the order of
25
ID0. It is equivalent to format of the Standard Identifier. The base ID defines the
Extended Frame's base priority.
ID28 to ID11.
24
shows the RTR bit logical value depending on frame type.
shows how the identifier written in the CAN_IRx register is transmitted to the CAN
23
RTR Bit Logical Value Depending on Frame Type
22
SRR IDE
ID[28:11] (Extended ID)
Arbitration Field
21
20
18-bit Identifier (Extended ID) RTR r1
19
18
17
16
15
14
13
12
RTR Bit Logical Value
Dominant
Recessive
11
Control Field
r0
10
9
DLC
8
7
ID[10:0] (Base ID)
6
5
Data Field
4
6048B–ATARM–29-Jun-06
3
2
1
0