Firmware User Manual (AE-step)
11
Revision 1.02
2019-04-24
TLE984x Firmware User Manual
BootROM Startup procedure
The watchdog is always disabled in debug support mode, except when the debug error loop is entered after a
boot error.
3.4
NAC Definition
The No Activity Counter (NAC) value defines the time window after reset release within the firmware is able to
receive BSL connection messages. If no BSL messages are received on the selected BSL interface during the
NAC window and NAC time has expired the firmware code proceeds to user mode.
NAC is a byte value which describes the timeout delay with a granularity of 5 ms. The NAC timeout supports a
maximum of 140 ms.
For example:
• NAC = 05
H
indicates a timeout delay of 25 ms (5
D
x 5 ms) before jumping to user mode
• NAC = 16
H
indicates a timeout delay of 110 ms (22
D
x 5 ms) before jumping to user mode
After ending the start up procedure, the program will detect any activity on the LIN/ FastLIN interface for the
remaining NAC window. When noactivity is detected, the program will jump to user mode. To determine the
minimum required NAC value, the baudrate, the interframe gap and the BSL passphrase requirements need
to be taken into account. For more details, refer to
“LIN / FastLIN Passphrase” on Page 20
In case a valid BSL passphrase is detected during the BSL window the firmware suspends the counting of the
WDT1 in order to avoid that requested BSL communication is broken by a WDT1 reset. The firmware will then
re-enable WDT1 before jumping to user code.
If NAC is 00
H
, the BSL window is closed, no BSL connection is possible and the user mode is entered without
delay.
If NAC is FF
H
, no timeout is used, BootROM code will switch off WDT1 and wait indefinitely for a BSLconnection
attempt.
3.5
User and BSL Mode Entry (UM)
Entry to user mode is determined by the No Activity Count (NAC) value,see
.
After waiting the time defined by the current NAC value, the startup procedure sets the VTOR register to point
to the beginning of the NVM (11000000
H
) and jumps to the reset handler. If a NVM double Bit error occurs when
reading the NAC value, the system goes into an endless loop waiting for BSL communication. Before entering
User mode (except for Hot Reset, see
Figure 3-2 “Flowchart – Start BootROM” on Page 13
frequency is switched to PLL output and to the max. frequency as stated in the datasheet. In case PLL has not
locked within 1 ms, the clock source fINTOSC/4 (20 MHz) will be used.
User mode is entered by jumping to the reset handler. This can happen directly from startup routine, after a
waiting time for possible BSL communication, or as a result of BSL commands. In all these cases, a jump to
user mode will only occur if the NVM content at 11000004
H
-11000007
H
is not FFFFFFFF
H
. Otherwise, the
BootROM executes an endless loop.
3.5.1
Unlock BSL Communications
The BootROM locks the BSL LIN and FastLIN communication after reset to avoid unexpected BSL
communication on the customer side. The host needs to unlock the communication by sending a passphrase
sequence to the BootROM.
Details about this passphrase and how it influences the NAC timeout are given in
