HC705V8GRSSLASHD datasheet(39/172 Pages) NXP

39 / 172 page

SECTION 3: EPROM AND EEPROM

Page 28

MC68HC705V8 Specification Rev. 2.1

Table 3-2:

Erase Mode Select

3.4.3

LATCH

When set, LATCH configures the EEPROM address and data bus for programming. When

LATCH is set, writes to the EEPROM array cause the data bus and the address bus to be

latched. This bit is readable and writable, but reads from the array are inhibited if the

LATCH bit is set and a write to the EEPROM space has taken place. When clear, address

and data buses are configured for normal operation. Reset clears this bit.

3.4.4

EERC - EEPROM RC Oscillator Control

When this bit is set, the EEPROM section uses the internal RC oscillator instead of the CPU

clock. After setting the EERC bit, delay a time t

RCON to allow the RC oscillator to stabilize.

This bit is readable and writable and should be set by the user when the internal bus

frequency falls below 1.5 MHz. Reset clears this bit.

3.4.5

EEPGM - EEPROM Programming Power Enable

EEPGM must be written to enable (or disable) the EEPGM function. When set, EEPGM

turns on the charge pump and enables the programming (or erasing) power to the

EEPROM array. When clear, this power is switched off. This will enable pulsing of the

programming voltage to be controlled internally. This bit can be read at any time, but can

only be written to if LATCH=1. If LATCH is not set, then EEPGM cannot be set. Reset clears

this bit.

3.4.6

PROGRAMMING/ERASING PROCEDURES

To program a byte of EEPROM, set LATCH = CPEN = 1, set ER1 = ER0 = 0, write data to

the desired address and then set EEPGM for a time t

EEPGM.

In general, all bits should be erased before being programmed. However, if write/erase

cycling is a concern, a procedure can be followed to minimize the cycling of each bit in each

EEPROM byte. The erased state is 1; therefore, if any bits within the byte need to be

changed from a 0 to a 1, the byte must be erased before programming. The decision

whether to erase a byte before programming is summarized in Table 3-3.

ER1

Bulk Erase

ER0

MODE

No Erase

Byte Erase

Block Erase

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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