User manual

Table Of Contents
Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 559
UG585 (v1.11) September 27, 2016
Chapter 18: CAN Controller
Configuration Registers
The CAN Controller Configuration register defines the configuration registers. This module allows
for read and write access to the registers through the APB interface. An overview of the CAN
controller registers are shown in section 18.3.8 Register Overview.
Transmit and Receive Messages
Separate storage buffers exist for transmit (TxFIFO) and receive (RxFIFO) messages through a FIFO
structure. Each buffer can store up to 64 messages. Once a message is written into the TxFIFO it takes
a total delay of 2*(Tx Driver delay + Propagation delay + Rx Driver delay) to transmit over the CAN
bus.
Tx High Priority Buffer
Each controller also has a transfer high priority buffer (TxHPB) provides storage for one transmit
message. Messages written on this buffer have maximum transmit priority. They are queued for
transmission immediately after the current transmission is complete, preempting any message in the
TxFIFO.
Acceptance Filters
Acceptance filters sort incoming messages with the user-defined acceptance mask and ID registers
to determine whether to store messages in the RxFIFO, or to acknowledge and discard them.
Messages passed through acceptance filters are stored in the RxFIFO.
18.1.4 Notices
Restrictions
There is a single PS clock generator for both controllers. When the internal clock is used, it will be of
the same clock frequency, but the clock to each controller can be individually enabled using the slcr
register, see section The Quad-SPI clock is divided down by at least two using the Quad-SPI baud
rate divider, see section 12.4.1 Clocks. In master mode, the SPI clock is divided down by at least four
using the SPI baud rate divider, see section 17.4.2 Clocks.. Also, either or both controllers can be
clocked from an external source via an MIO pin, see section 18.4.1 Clocks.
RECOMMENDED: For all clocking sources, set the can.BRPR register to a value of 2 or greater and a
prescaler value of at least 3.