PXR40RM Datasheet, PDF (291/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Boot Assist Module (BAM)
N R Z S ignal
SYNC_SEG
TIM E SEG M EN T 1
TIM E SEG M EN T 2
1 time quanta
Transmit Point
9 time quanta
1 Bit Time
2 time quanta
Sample Point
Note: 1 Time quanta = 5 System clock periods
Figure 9-6. CAN Bit timing
The BAM program ignores CAN errors and all received messages are assumed to be good. Received
messages are transmitted back. The host processor must compare the MCU transmissions with the sent
data and restart the process if an error is detected.
9.5.5.2 SCI Controller Configuration in Fixed Baud Rate Mode
The eSCI is configured for 1 start bit, 8 data bits, no parity, 1 stop bit and operates at a baud rate equal to
system clock divided by 1248. See Table 9-8 for examples of baud rates.
The BAM program ignores the eSCI errors: All data received is assumed to be good and is sent back
through the TXD pin. The host processor must compare the MCU transmitted data with the sent data and
restart the process if an error is detected.
9.5.5.3 Serial Boot Mode Download Protocol
The download protocol follows four steps:
1. Host sends 64-bit password.
2. Host sends start address, size of download code in bytes, and VLE bit.
3. Host sends the application code data.
4. The MCU switches to the loaded code at the start address.
The communication is done in half-duplex manner; any transmission from host is followed by the MCU
transmission. The host computer should not send data until it receives echo from the MCU. All multi byte
data structures must be sent most-significant byte (MSB) first.
When the CAN is used for serial download, the data is packed into standard CAN messages in the
following manner:
• A message with 0x11 ID and 8-byte length to send the password. The MCU transmits back the
same data, but with ID of 0x1.
• A message with 0x12 ID and 8-byte length to send the start address, length, and the VLE mode bit.
The MCU transmits back the same data, but with ID of 0x2.
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
9-11