HI-3200, HI-3201
Channel Repetition Period
CAN REPETITION RATE REGISTER
(Address 0x8033)
7
6
5
4
3
2
1
0
LSB
MSB
The Repetition rate register value defines the time
interval between successive starts of the programmed
CAN transmit sequence. The value is set in binary, with
the LSB representing 10 ms.
When the Repetition Rate counter is programmed to zero
(default), the transmit sequence shall execute one time
only. A zero - to - one transition of the RUN/STOP bit will
cause the transmit sequence to start. One-time execution
of the sequencer is useful when transmitting CAN frames
directly from the host CPU. One or more immediate-
mode (Type 1) descriptors can be written into the
sequence table, transmitted, and then refreshed for the
next cycle.
If the repetition rate is shorter than the minimum time
needed to transmit all CAN frames in the sequence (but
not zero), the transmit sequence will begin again
immediately if the CAN Control Register SKIP bit is a
zero. If the SKIP bit is a one, the sequencer will wait until
the next rollover of the Repetition Rate Counter before
starting a new cycle.
CAN Bus Transmit Descriptor Table
0x79BF
Repetion Rate
Register
End of Sequence marker
Transmit Frame Descriptor n
Repetition rate
counter
Descriptor Byte n
0 - 24 Bytes
Transmit Frame Descriptor 5
Transmit Frame Descriptor 4
Transmit Frame Descriptor 3
Transmit Frame Descriptor 2
}
Descriptor Byte 2
Descriptor Byte 1
Descriptor Header
Transmit Frame Descriptor 1
Transmit Frame Descriptor 0
Sequence
pointer
0x6000
The contents of each CAN frame transmitted in the
sequence is defined by its Frame Descriptor. Each
descriptor consists of one “Descriptor Header Byte” and
from 0 to 24 additional descriptor bytes depending upon,
the descriptor type (type 1 - 3) and the data payload
length. A special descriptor header marks the end of the
descriptor table.
The three different descriptor types allow the user to
make best use of the available descriptor table memory
space while still allowing complete flexibility in defining
frame content and data source. The Descriptor header
byte is of a common format for all three descriptor types.
The CAN Transmit sequence pointer uses information in
the header byte to determine the length of the descriptor
and thus the address of the next descriptor block in the
sequence table.
HOLT INTEGRATED CIRCUITS
33
HOLTIC [ HOLT INTEGRATED CIRCUITS ]
