mc9s08sg4 Freescale Semiconductor, Inc, mc9s08sg4 Datasheet - Page 54

• Manufacturer Part Number: mc9s08sg4
• Description: 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

Chapter 4 Memory
control registers (FOPT, FPROT) at reset. There is also an 8-byte comparison key in FLASH memory.
Refer to
refers to registers and control bits only by their names. A Freescale Semiconductor-provided equate or
header file normally is used to translate these names into the appropriate absolute addresses.
4.7.1
Bit 7 of this register is a read-only flag. Bits 6:0 may be read at any time but can be written only one time.
Before any erase or programming operations are possible, write to this register to set the frequency of the
clock for the nonvolatile memory system within acceptable limits.
Table 4-7
54
Reset
PRDIV8
DIVLD
Field
DIV
5:0
7
6
W
R
Table 4-3
shows the appropriate values for PRDIV8 and DIV for selected bus frequencies.
DIVLD
FLASH Clock Divider Register (FCDIV)
Divisor Loaded Status Flag — When set, this read-only status flag indicates that the FCDIV register has been
written since reset. Reset clears this bit and the first write to this register causes this bit to become set regardless
of the data written.
0 FCDIV has not been written since reset; erase and program operations disabled for FLASH.
1 FCDIV has been written since reset; erase and program operations enabled for FLASH.
Prescale (Divide) FLASH Clock by 8
0 Clock input to the FLASH clock divider is the bus rate clock.
1 Clock input to the FLASH clock divider is the bus rate clock divided by 8.
Divisor for FLASH Clock Divider — The FLASH clock divider divides the bus rate clock (or the bus rate clock
divided by 8 if PRDIV8 = 1) by the value in the 6-bit DIV field plus one. The resulting frequency of the internal
FLASH clock must fall within the range of 200 kHz to 150 kHz for proper FLASH operations. Program/Erase
timing pulses are one cycle of this internal FLASH clock which corresponds to a range of 5 μs to 6.7 μs. The
automated programming logic uses an integer number of these pulses to complete an erase or program
operation. See
0
7
and
= Unimplemented or Reserved
Table 4-4
PRDIV8
Equation 4-1
0
6
if PRDIV8 = 1 — f
Figure 4-5. FLASH Clock Divider Register (FCDIV)
if PRDIV8 = 0 — f
Table 4-6. FCDIV Register Field Descriptions
for the absolute address assignments for all FLASH registers. This section
MC9S08SG8 MCU Series Data Sheet, Rev. 3
and
0
5
Equation
FCLK
FCLK
4-2.
= f
0
4
= f
Bus
Description
Bus
÷ (8 × (DIV + 1))
÷ (DIV + 1)
3
0
DIV
0
2
Freescale Semiconductor
0
1
Eqn. 4-1
Eqn. 4-2
0
0