MFM8126S-70/90/12
ISSUE4.2:November1998
CommandDefinitions
Device operations are selected by writing specific address and data sequences into the command register. The
following table defines these register command sequences.
Bus
First Bus
Second Bus Third bus
Fourth bus
Fifth Bus
Sixth Bus
Write Write Cycle Write Cycle Write Cycle Read/Write
Write Cycle Write Cycle
COMMAND
SEQUENCE
Cycle
Req'd
Cycle
Addr Data Addr Data Addr Data Addr Data Addr Data Addr
Data
Read/Reset
4
5555H
AAH 2AAAH
55H
5555H
F0H
RA
RD
Autoselect
4
4
5555H
5555H
AAH 2AAAH
AAH 2AAAH
55H
55H
5555H
5555H
90H 00H/01H 01H/20H
Byte Program
A0H
PA
PD
Chip erase
6
6
5555H
5555H
AAH 2AAAH
AAH 2AAAH
55H
55H
5555H
5555H
80H
80H
5555H
5555H
AAH 2AAAH
AAH 2AAAH
55H
55H
5555H
SA
10H
30H
Sector erase
NOTES:
1. Address bit A15=X=Don't care. Write Sequences may be initiated with A15 in either state.
2. Address bit A16=X=Don't care for all address commands except for Program Address (PA) and Sector
Address (SA).
3. RA=Address of the memory location to be read.
PA=Address of memory location to be programmed. Addresses are latched on the falling edge of the WE
pulse.
SA=Address of the sector to be erased. The combination of A16, A15 and A14 will uniquely select any
sector.
4. RD=DatareadfromlocationRAduringreadoperation.
PD=Data to be programmed at location PA. Data is latched on the falling edge of WE
Read/Reset Command
The read or reset operation is initiated by writing the read/reset command sequence into the command
register. Microprocessor read cycles retrieve array data from the memory. The device remains enabled for
reads until the command register contents are altered.
The device will automatically power-up in the read/reset state. In this case, a command sequence is not
required to read data. Standard microprocessor read cycles will retrieve array data. This default value ensures
that no spurious alteration of memory content occurs during the power transition. Refer to the AC Read Char-
acteristics and Waveforms for specific timing parameters.
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MOSAIC [ MOSAIC ]
