NXP Semiconductors MPC5644A, Reference Manual, Page: 1447 / 1735

FlexRay Communication Controller (FlexRay)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 1447
33.2.1.2 FR_A_TX — Transmit Data Channel A
The FR_A_TX signal carries the transmit data for channel A to the corresponding FlexRay bus driver.
33.2.1.3 FR_A_TX_EN — Transmit Enable Channel A
The FR_A_TX_EN signal indicates to the FlexRay bus driver that the CC is attempting to transmit data
on channel A.
33.2.1.4 FR_B_RX — Receive Data Channel B
The FR_B_RX signal carries the receive data for channel B from the corresponding FlexRay bus driver.
33.2.1.5 FR_B_TX — Transmit Data Channel B
The FR_B_TX signal carries the transmit data for channel B to the corresponding FlexRay bus driver
33.2.1.6 FR_B_TX_EN — Transmit Enable Channel B
The FR_B_TX_EN signal indicates to the FlexRay bus driver that the CC is attempting to transmit data
on channel B.
33.2.1.7 FR_DBG[3], FR_DBG[2], FR_DBG[1], FR_DBG[0] — Strobe Signals
These signals provide the selected debug strobe signals. For details on the debug strobe signal selection
refer to
Section 33.6.16, Strobe signal support” .
33.3 Controller host interface clocking
The clock for the CHI is derived from the system bus clock and has the same phase and frequency as the
system bus clock. There are two constraints for the minimum CHI clock frequency:
• The first constraint corresponds to the number of utilized message buffers and is specified in
Section 33.7.6, Number of usable message buffers ”.
• The second constraint corresponds to the value of the TIMEOUT field in the System Memory
Access Time-Out Register (FR_SYMATOR) and is specified in Section 33.7.1.1, Configure
System Memory Access Time-Out Register (FR_SYMATOR) ”.
33.4 Protocol engine clocking
The clock for the protocol engine can be generated by two sources. The first source is the internal crystal
oscillator and the second source is an internal PLL. The clock source to be used is selected by the clock
source select bit CLKSEL in the
Module Configuration Register (FR_MCR) .