MC68HC11EA9 Datasheet, PDF (18/58 Pages) Motorola, Inc – 8 BIT HCMOS SINGLE CHIP MICROCONTOROLLER WITH A/D CONVERTER

Freescale Semiconductor, Inc.
ERASE — Erase/Normal Control for EEPROM
Refer to 4.10 EEPROM.
EELAT — EEPROM Latch Control
0 = EEPROM address and data bus configured for normal reads
1 = EEPROM address and data bus configured for programming or erasing
PGM — EPROM/OTPROM/EEPROM Programming Voltage Enable
0 = Programming voltage to EPROM/OTPROM/EEPROM array disconnected
1 = Programming voltage to EPROM/OTPROM/EEPROM array connected
PGM can be read any time and can only be written when ELAT = 1 (for EPROM/OTPROM program-
ming) or when EELAT = 1 (for EEPROM programming).
4.10 EEPROM
MC68HC(7)11EA9 MCUs contain 512 bytes of EEPROM. The 512-byte EEPROM is initially located at
$B600 after reset, assuming EEPROM is enabled in the memory map by the EEON bit in the CONFIG
register. EEPROM can be placed at any 4 Kbyte boundary ($x600) by writing appropriate values to the
INIT register. Note that EEPROM can be mapped such that it contains the vector space. See Figure 6.
4.10.1 Programming and Erasing EEPROM
Programming and erasing the EEPROM is controlled by the PPROG register, and is dependent upon
the block protect (BPROT) register value. The erased state of an EEPROM bit is one. During a read
operation, bit lines are precharged to one. The floating gate devices of programmed bits conduct and
pull the bit lines to zero. Unprogrammed bits remain at the precharged level and are read as ones. Pro-
gramming a bit to one causes no change. Programming a bit to zero changes the bit so that subsequent
reads return zero.
When appropriate bits in the BPROT register are cleared, the PPROG register controls programming
and erasing of the EEPROM. The PPROG register can be read or written at any time, but logic enforces
defined programming and erasing sequences to prevent unintentional changes to data in EEPROM.
When the EELAT bit in the PPROG register is cleared, the EEPROM can be read as if it were a ROM.
The on-chip charge pump that generates the EEPROM programming voltage from V_DD uses MOS ca-
pacitors, which are relatively small in value. The efficiency of this charge pump and its drive capability
are affected by the level of V_DD and the frequency of the driving clock. The clock source driving the
charge pump is software selectable. When the clock select (CSEL) bit in the OPTION register is zero,
the E clock is used; when CSEL is one, an on-chip resistor-capacitor (RC) oscillator is used. The RC
oscillator should be used when E < 1 MHz. This RC oscillator will drive the A/D circuitry as well as the
EEPROM charge pump when CSEL = 1.
The EEPROM programming voltage connection to the EEPROM array is not enabled until there has
been a write to PPROG with EELAT set and PGM cleared. This must be followed by a write to a valid
EEPROM location or to the CONFIG address, and then a write to PPROG with both EELAT and PGM
set. Any attempt to set both EELAT and PGM during the same write operation results in neither bit being
set.
The erased state of an EEPROM byte is $FF (all ones).
To erase the EEPROM, ensure that the proper bits of the BPROT register are cleared, then complete
the following steps using the PPROG register:
1. Set the ERASE, EELAT, and appropriate BYTE and ROW bits in PPROG register.
2. Write to the appropriate EEPROM address with any data. Row erase only requires a write to
any location in the row. Bulk erase is done by writing to any location in the array.
3. Set the ERASE, EELAT, EEPGM, and appropriate BYTE and ROW bits in PPROG register.
MC68HC11EA9
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