
Boot Assist Module (BAM)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
631
When the Fixed Baud Rate mode is selected, the BAM program configures the SCI_A_RX pin to be the
input of the eSCI_A module, CN_A_RX pin as an input, and CN_A_TX as an output of the CAN_A
module.
When Baud Rate Detection Mode is selected, the BAM program configures SCI_A_RX and CN_A_RX
pins as GPI inputs for polling their state by the CPU.
shows the configuration summary for theSCI and CAN controllers pins.
The BAM configures the communication modules for reception with fixed baud rates as shown in the
and waits for data reception.
.
Table 21-7. CAN/eSCI pins configuration for CAN/eSCI fixed baud rate boot modes
Pins
Reset
function
Initial Serial Boot Mode
Serial Boot Mode after a
valid CAN message received
Serial Boot Mode after a
valid eSCI message
received
Function
Pad
configuration
Function
Pad
configuration
Function
Pad
configuration
CN_A_TX
GPIO
CN_A_TX
Push/Pull
output, with
medium slew
rate
CN_A_TX
Push/Pull
output, with
medium slew
rate
GPIO
—
CN_A_RX
GPIO
CN_A_RX
Input with
pull-up and
hysteresis
CN_A_RX
Input with
pull-up and
hysteresis
GPIO
—
SCI_A_T
X
GPIO
GPIO
—
GPIO
—
SCI_A_TX
Push/Pull
output, with
medium slew
rate
SCI_A_R
X
GPIO
SCI_A_R
X
Input with
pull-up and
hysteresis
GPIO
—
SCI_A_R
X
Input with
pull-up and
hysteresis
Table 21-8. Serial boot mode – baud rate & watchdog summary
Crystal
frequency
(MHz)
System
Clock
frequency
(MHz)
Desired
eSCI Baud
rate
(baud)
Actual
eSCI Baud
rate
(baud)
eSCI
error (%)
CAN
Baud
rate
(baud)
Core Watchdog
1
timeout period
(s)
1
The SWT is used as a watchdog during serial boot mode, but the core watchdog is enabled just before switching
to the user application to provide compatibility with earlier MPC55XX parts.
SWT timeout
period during
serial boot
(s)
f
xtal
f
sys
= f
xtal
f
sys
/ 833.33
f
sys
/ 832
—
f
sys
/ 40
2.5 * 2
27
/ f
sys
223696213 / f
sys
8
8
9600 9615.4
0.16
200K
42
27.96
12
12
14400 14423.
0
0.16
300K
28
18.64
16
16
19200 19230.8
0.16
400K
21
13.98
20
20
24000 24038.5
0.16
500K
16.8
11.18
Summary of Contents for MPC5644A
Page 2: ...MPC5644A Microcontroller Reference Manual Rev 6 2 Freescale Semiconductor...
Page 24: ...MPC5644A Microcontroller Reference Manual Rev 6 24 Freescale Semiconductor...
Page 26: ...MPC5644A Microcontroller Reference Manual Rev 6 26 Freescale Semiconductor...
Page 52: ...Introduction MPC5644A Microcontroller Reference Manual Rev 6 52 Freescale Semiconductor...
Page 56: ...Memory Map MPC5644A Microcontroller Reference Manual Rev 6 56 Freescale Semiconductor...
Page 1228: ...Decimation Filter MPC5644A Microcontroller Reference Manual Rev 6 1228 Freescale Semiconductor...
Page 1440: ...FlexCAN Module MPC5644A Microcontroller Reference Manual Rev 6 1440 Freescale Semiconductor...