mc9s12c32mpb16 Freescale Semiconductor, Inc, mc9s12c32mpb16 Datasheet - Page 172

• Manufacturer Part Number: mc9s12c32mpb16
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 6 Background Debug Module (BDMV4) Block Description
172
CLKSW
UNSEC
Field
PLLSEL
2
1
0
0
1
1
Clock Switch — The CLKSW bit controls which clock the BDM operates with. It is only writable from a hardware
BDM command. A 150 cycle delay at the clock speed that is active during the data portion of the command will
occur before the new clock source is guaranteed to be active. The start of the next BDM command uses the new
clock for timing subsequent BDM communications.
Table 6-3
and reset generator) bits.
Note: The BDM alternate clock source can only be selected when CLKSW = 0 and PLLSEL = 1. The BDM serial
Note: If the acknowledge function is turned on, changing the CLKSW bit will cause the ACK to be at the new rate
Unsecure — This bit is only writable in special single-chip mode from the BDM secure firmware and always gets
reset to zero. It is in a zero state as secure mode is entered so that the secure BDM firmware lookup table is
enabled and put into the memory map along with the standard BDM firmware lookup table.
The secure BDM firmware lookup table verifies that the on-chip EEPROM and FLASH EEPROM are erased. This
being the case, the UNSEC bit is set and the BDM program jumps to the start of the standard BDM firmware
lookup table and the secure BDM firmware lookup table is turned off. If the erase test fails, the UNSEC bit will
not be asserted.
0 System is in a secured mode
1 System is in a unsecured mode
Note: When UNSEC is set, security is off and the user can change the state of the secure bits in the on-chip
interface is now fully synchronized to the alternate clock source, when enabled. This eliminates frequency
restriction on the alternate clock which was required on previous versions. Refer to the device overview
section to determine which clock connects to the alternate clock source input.
for the write command which changes it.
FLASH EEPROM. Note that if the user does not change the state of the bits to “unsecured” mode, the
system will be secured again when it is next taken out of reset.
CLKSW
shows the resulting BDM clock source based on the CLKSW and the PLLSEL (Pll select from the clock
0
1
0
1
Table 6-2. BDMSTS Field Descriptions (continued)
Bus clock
Bus clock
Alternate clock (refer to the device overview chapter to determine the alternate clock
source)
Bus clock dependent on the PLL
MC9S12C-Family / MC9S12GC-Family
Table 6-3. BDM Clock Sources
Rev 01.23
Description
BDMCLK
Freescale Semiconductor