DSPIC30F5011-20I/PTG Microchip Technology, DSPIC30F5011-20I/PTG Datasheet - Page 115

• Manufacturer Part Number: DSPIC30F5011-20I/PTG
• Description: IC, DSC, 16BIT, 66KB, 40MHZ 5.5V TQFP-64
• Manufacturer: Microchip Technology
• Series: DsPIC30Fr

Specifications of DSPIC30F5011-20I/PTG

• Core Frequency: 40MHz
• Core Supply Voltage: 5.5V
• Embedded Interface Type: CAN, I2C, SPI, UART
• No. Of I/o's: 52
• Flash Memory Size: 66KB
• Supply Voltage Range: 2.5V To 5.5V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

17.6.2
There is a programmable prescaler with integral values
ranging from 1 to 64, in addition to a fixed divide-by-2
for clock generation. The time quantum (T
unit of time derived from the oscillator period, and is
given by Equation 17-1, where F
CANCKS bit is set) or 4F
EQUATION 17-1:
17.6.3
This part of the bit time is used to compensate physical
delay times within the network. These delay times
consist of the signal propagation time on the bus line
and the internal delay time of the nodes. The Prop Seg
can be programmed from 1 T
PRSEG<2:0> bits (CiCFG2<2:0>).
17.6.4
The phase segments are used to optimally locate the
sampling of the received bit within the transmitted bit
time. The sampling point is between Phase1 Seg and
Phase2 Seg. These segments are lengthened or
shortened by resynchronization. The end of the
Phase1 Seg determines the sampling point within a bit
period. The segment is programmable from 1 T
8 T
transmitted
programmable from 1 T
to be equal to the greater of Phase1 Seg or the
information processing time (2 T
initialized
(CiCFG2<5:3>), and Phase2 Seg is initialized by
setting SEG2PH<2:0> (CiCFG2<10:8>).
The following requirement must be fulfilled while setting
the lengths of the phase segments:
© 2008 Microchip Technology Inc.
Note:
Q
Prop Seg + Phase1 Seg > = Phase2 Seg
. Phase2 Seg provides delay to the next
PRESCALER SETTING
F
CANCKS = 0, then F
7.5 MHz.
PROPAGATION SEGMENT
PHASE SEGMENTS
T
CAN
by
data
Q
= 2 (BRP<5:0> + 1) / F
must not exceed 30 MHz. If
setting
transition.
TIME QUANTUM FOR
CLOCK GENERATION
Q
CY
to 8 T
(if CANCKS is clear).
Q
bits
Q
Q
to 8 T
, or it may be defined
CY
). The Phase1 Seg is
The
CAN
must not exceed
CAN
Q
SEG1PH<2:0>
is F
by setting the
segment
Q
) is a fixed
CY
(if the
Q
to
is
17.6.5
The sample point is the point of time at which the bus
level is read and interpreted as the value of that
respective bit. The location is at the end of Phase1
Seg. If the bit timing is slow and contains many T
possible to specify multiple sampling of the bus line at
the sample point. The level determined by the CAN bus
then corresponds to the result from the majority
decision of three values. The majority samples are
taken at the sample point and twice before with a
distance of T
choose between sampling three times at the same
point or once at the same point, by setting or clearing
the SAM bit (CiCFG2<6>).
Typically, the sampling of the bit should take place at
about 60-70% through the bit time, depending on the
system parameters.
17.6.6
To compensate for phase shifts between the oscillator
frequencies of the different bus stations, each CAN
controller must be able to synchronize to the relevant
signal edge of the incoming signal. When an edge in
the transmitted data is detected, the logic will compare
the location of the edge to the expected time (Synchro-
nous Segment). The circuit will then adjust the values
of Phase1 Seg and Phase2 Seg. There are 2
mechanisms used to synchronize.
17.6.6.1
Hard synchronization is only done whenever there is a
‘recessive’ to ‘dominant’ edge during bus Idle indicating
the start of a message. After hard synchronization, the
bit time counters are restarted with the Sync Seg. Hard
synchronization forces the edge which has caused the
hard synchronization to lie within the synchronization
segment of the restarted bit time. If a hard
synchronization is done, there will not be a
resynchronization within that bit time.
17.6.6.2
As a result of resynchronization, Phase1 Seg may be
lengthened or Phase2 Seg may be shortened. The
amount of lengthening or shortening of the phase
buffer segment has an upper bound known as the
synchronization jump width, and is specified by the
SJW<1:0> bits (CiCFG1<7:6>). The value of the
synnschronization jump width will be added to Phase1
Seg
resynchronization
between 1 T
The following requirement must be fulfilled while setting
the SJW<1:0> bits:
dsPIC30F5011/5013
Phase2 Seg > Synchronization Jump Width
or
subtracted
SAMPLE POINT
SYNCHRONIZATION
Q
Q
Hard Synchronization
Resynchronization
and 4 T
/2. The CAN module allows the user to
jump
Q
.
from
width
Phase2
DS70116H-page 115
is
programmable
Seg.
Q
, it is
The