ISSUE 4.2:November1998
MFM8126S-70/90/12
Toggle Bit - D6
The MFM8126 also features the "toggle bit" as a method to indicate to the host system that the Embedded
Algorithms are in progress or completed.
During an Embedded Program or Erase Algorithm cycle, successive attempts to read (OE Toggling) data from
the device will result in D6 toggling between one and zero. Once the Embedded Program or Erase Algorithm
cycle is completed, D6 will stop toggling and valid data will be read on successive attempts. During program-
ming, the Toggle bit is valid after the rising edge of the forth WE pulse in the four write pulse sequence. For chip
erase, the Toggle bit is valid after the sixth WE pulse in the six write pulse sequence.
For sector erase, the Toggle bit is valid after the last rising edge of the sector erase WE pulse. The Toggle Bit
is active during the sector time-out. Note: CS or OE toggling will toggle D6.
Exceeding Time Limits - D5
D5 will indicate if the program or erase time has exceeded the specified limits. Under these conditions D5 will
produce "1", indicating the program or erase cycle was not successfully completed . Data Polling is the only
operating function of the device under this condition. The CS circuit will partially power down the device under
these conditions (to approximately 2mA). The OE and WE pins will control the output disable functions . To
reset the device, write reset command sequence to the device. This allows the system to continue to use the
other active sectors in the device.
If this failiure condition occurs during the sector erase operation, it specifies that a particular sector is bad and
it may not be reused. However, other sectors are still functional and may be used for additional program or erase
operations. The device must be reset to use other sectors. Write the Reset command sequence to the device,
and then execute the program or erase command sequence.
If this failure condition occurs during the chip erase operation, it specifies that the entire chip is bad or
combination of sectors are bad.
If this failure condition occurs during the byte programming operation, it specifies that the entire sector
containing that byte is bad and this sector may not be reused (other sectors are still functional and can be
reused). The device must be reset to use other sectors.
The D5 failure condition may also appear if a user tries to program a non blank location without erasing. In this
case the system never reads valid data on the D7 bit and D6 never stops toggling. Once the device has exceeded
timing limits, the D5 bit will indicate a "1". Please note that this is not a device failure condition since the device
was incorrectly used. The device must be reset to continue using the device.
Hardware Sequence Flag - D4
If the device has exceeded the specified erase or program time and D5 is "1", then D4 will indicate at which step
in the algorithm the device exceeded the limits. A "0" in D4 indicates in programming, a "1" indicates an erase.
Sector Erase Timer - D3
After the completion of the initial sector erase command sequence the sector erase time-out will begin. D3 will
remain low until the time-out is complete. Data Polling and Toggle Bit are valid after the initial sector erase
commandsequence.
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MOSAIC [ MOSAIC ]
