68HC908RF datasheet(30/188 Pages) MOTOROLA

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Memory

Data Sheet

MC68HC908RF2 — Rev. 4.0

Memory

MOTOROLA

BLK0 — Block Erase Control Bit

This read/write bit together with BLK1 allows erasing of blocks of varying size.

See 2.5.3 FLASH 2TS Erase Operation for a description of available block

sizes.

HVEN — High-Voltage Enable Bit

This read/write bit enables the charge pump to drive high voltages for program

and erase operations in the array. HVEN can be set only if either PGM = 1 or

ERASE = 1 and the proper sequence for smart programming or erase is

followed.

1 = High voltage enabled to array and charge pump on

0 = High voltage disabled to array and charge pump off

MARGIN — Margin Read Control Bit

This read/write bit configures the memory for margin read operation. MARGIN

cannot be set if the HVEN = 1. MARGIN will automatically return to unset (0) if

asserted when HVEN = 1.

1 = Margin read operation selected

0 = Margin read operation unselected

ERASE — Erase Control Bit

This read/write bit configures the memory for erase operation. ERASE is

interlocked with the PGM bit such that both bits cannot be set at the same time.

1 = Erase operation selected

0 = Erase operation unselected

PGM — Program Control Bit

This read/write bit configures the memory for program operation. PGM is

interlocked with the ERASE bit such that both bits cannot be set at the same

time.

1 = Program operation selected

0 = Program operation unselected

2.5.2 FLASH 2TS Charge Pump Frequency Control

The internal charge pump, required for program, margin read, and erase

operations, is designed to operate most efficiently with a 2-MHz clock. The charge

pump clock is derived from the bus clock. Table 2-2 shows how the FDIV bits are

used to select a charge pump frequency based on the bus clock frequency.

Program, margin read, and erase operations cannot be performed if the bus clock

frequency is below 2 MHz.

NOTE:

The charge pump is optimized for 2-MHz operation.

Table 2-2. Charge Pump Clock Frequency

FDIV0

Pump Clock Frequency

Bus frequency

÷ 1

Bus frequency

÷ 2

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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