S9S12XS256J0CAL Datasheet, PDF (535/738 Pages) Freescale Semiconductor, Inc – Microcontrollers

256 KByte Flash Module (S12XFTMR256K1V1)
Offset Module Base + 0x0013
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 18-25. Flash Reserved4 Register (FRSV4)
All bits in the FRSV4 register read 0 and are not writable.
18.4 Functional Description
18.4.1 Flash Command Operations
Flash command operations are used to modify Flash memory contents.
The next sections describe:
• How to write the FCLKDIV register that is used to generate a time base (FCLK) derived from
OSCCLK for Flash program and erase command operations
• The command write sequence used to set Flash command parameters and launch execution
• Valid Flash commands available for execution
18.4.1.1 Writing the FCLKDIV Register
Prior to issuing any Flash program or erase command after a reset, the user is required to write the
FCLKDIV register to divide OSCCLK down to a target FCLK of 1 MHz. Table 18-7 shows recommended
values for the FDIV field based on OSCCLK frequency.
NOTE
Programming or erasing the Flash memory cannot be performed if the bus
clock runs at less than 1 MHz. Setting FDIV too high can destroy the Flash
memory due to overstress. Setting FDIV too low can result in incomplete
programming or erasure of the Flash memory cells.
When the FCLKDIV register is written, the FDIVLD bit is set automatically. If the FDIVLD bit is 0, the
FCLKDIV register has not been written since the last reset. If the FCLKDIV register has not been written,
any Flash program or erase command loaded during a command write sequence will not execute and the
ACCERR bit in the FSTAT register will set.
S12XS Family Reference Manual, Rev. 1.13
Freescale Semiconductor
535