MCP2510-ESO MICROCHIP [Microchip Technology], MCP2510-ESO Datasheet - Page 38

• Manufacturer Part Number: MCP2510-ESO
• Description: Stand-Alone CAN Controller with SPI Interface
• Manufacturer: MICROCHIP [Microchip Technology]

MCP2510
FIGURE 5-3: Shortening a Bit Period
5.8
Some requirements for programming of the time seg-
ments:
• Prop Seg + Phase Seg 1 >= Phase Seg 2
• Prop Seg + Phase Seg 1 >= T
• Phase Seg 2 > Sync Jump Width
For example, assuming that a 125 kHz CAN baud rate
with F
T
500nsec. To obtain 125 kHz, the bit time must be 16
T
Typically, the sampling of the bit should take place at
about 60-70% of the bit time, depending on the system
parameters. Also, typically, the T
Sync Seg = 1 T
Seg 1 = 7 T
transition. This would leave 6 T
Since Phase Seg 2 is 6, by the rules, SJW could be the
maximum of 4 T
only necessary when the clock generation of the differ-
ent nodes is inaccurate or unstable, such as using
ceramic resonators. So an SJW of 1 is typically
enough.
DS21291C-page 38
OSC
Q
.
T
Input Signal
Q
OSC
= 50 nsec, choose BRP<5:0> = 04h, then T
Programming Time Segments
= 20 MHz is desired:
Sync
Q
would place the sample at 10 T
Q
Q
; Prop Seg = 2 T
. However, normally a large SJW is
Segment
Prop
Q
DELAY
DELAY
for Phase Seg 2.
Q
; So setting Phase
is 1-2 T
Segment 1
Phase
Q
after the
Q
.
Preliminary
Q
=
Sample
Point
5.9
The bit timing requirements allow ceramic resonators
to be used in applications with transmission rates of up
to 125 kbit/sec, as a rule of thumb. For the full bus
speed range of the CAN protocol, a quartz oscillator is
required. A maximum node-to-node oscillator variation
of 1.7% is allowed.
Oscillator Tolerance
Segment 2
Phase
Bit Length
2000 Microchip Technology Inc.
Actual
SJW
Bit Length
Nominal