NVM_FCLKDIV field descriptions
Field
Description
7
FDIVLD
Clock Divider Loaded
0
FCLKDIV register has not been written since the last reset.
1
FCLKDIV register has been written since the last reset.
6
FDIVLCK
Clock Divider Locked
0
FDIV field is open for writing.
1
FDIV value is locked and cannot be changed. After the lock bit is set high, only reset can clear this bit
and restore writability to the FDIV field in user mode.
FDIV
Clock Divider Bits
FDIV[5:0] must be set to effectively divide BUSCLK down to 1MHz to control timed events during flash
program and erase algorithms. Refer to the table in the
for the
recommended values of FDIV based on the BUSCLK frequency.
4.6.2 Flash Security Register (NVM_FSEC)
The FSEC register holds all bits associated with the security of the MCU and NVM
module. All bits in the FSEC register are readable but not writable. During the reset
sequence, the FSEC register is loaded with the contents of the flash security byte in the
flash configuration field at global address 0xFF7F located in flash memory.
See
Address: 3020h base + 1h offset = 3021h
Bit
7
6
5
4
3
2
1
0
Read
Write
Reset
* Notes:
x = Undefined at reset.
•
NVM_FSEC field descriptions
Field
Description
7–6
KEYEN
Backdoor Key Security Enable Bits
The KEYEN[1:0] bits define the enabling of backdoor key access to the flash module.
NOTE: 01 is the preferred KEYEN state to disable backdoor key access.
00
Disabled
01
Disabled
10
Enabled
11
Disabled
Table continues on the next page...
Chapter 4 Memory map
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
NXP Semiconductors
87
Summary of Contents for MC9S08PA4
Page 1: ...MC9S08PA4 Reference Manual Supports MC9S08PA4 Document Number MC9S08PA4RM Rev 5 08 2017 ...
Page 2: ...MC9S08PA4 Reference Manual Rev 5 08 2017 2 NXP Semiconductors ...
Page 22: ...MC9S08PA4 Reference Manual Rev 5 08 2017 22 NXP Semiconductors ...
Page 28: ...System clock distribution MC9S08PA4 Reference Manual Rev 5 08 2017 28 NXP Semiconductors ...
Page 150: ...Port data registers MC9S08PA4 Reference Manual Rev 5 08 2017 150 NXP Semiconductors ...
Page 196: ...Human machine interfaces HMI MC9S08PA4 Reference Manual Rev 5 08 2017 196 NXP Semiconductors ...
Page 224: ...Instruction Set Summary MC9S08PA4 Reference Manual Rev 5 08 2017 224 NXP Semiconductors ...
Page 232: ...Functional Description MC9S08PA4 Reference Manual Rev 5 08 2017 232 NXP Semiconductors ...
Page 258: ...FTM Interrupts MC9S08PA4 Reference Manual Rev 5 08 2017 258 NXP Semiconductors ...
Page 294: ...Functional description MC9S08PA4 Reference Manual Rev 5 08 2017 294 NXP Semiconductors ...
Page 398: ...Resets MC9S08PA4 Reference Manual Rev 5 08 2017 398 NXP Semiconductors ...
Page 400: ...MC9S08PA4 Reference Manual Rev 5 08 2017 400 NXP Semiconductors ...