Intel
£
Advanced+ Boot Block Flash Memory (C3)
Datasheet 21
The contents of the status register are latched on the falling edge of OE# or CE# (whichever occurs
last) which prevents possible bus errors that might occur if Status Register contents change while
being read. CE# or OE# must be toggled with each subsequent status read, or the Status Register
will not indicate completion of a Program or Erase operation.
When the WSM is active, SR[7] will indicate the status of the WSM; the remaining bits in the
status register indicate whether the WSM was successful in performing the preferred operation (see
Table 9, “Status Register Bit Definition” on page 26).
4.1.4.1 Clear Status Register
The WSM can set Status Register bits 1 through 7 and can clear bits 2, 6, and 7; but, the WSM
cannot clear Status Register bits 1, 3, 4 or 5. Because bits 1, 3, 4, and 5 indicate various error
conditions, these bits can be cleared only through the Clear Status Register (0x50) command. By
allowing the system software to control the resetting of these bits, several operations may be
performed (such as cumulatively programming several addresses or erasing multiple blocks in
sequence) before reading the status register to determine if an error occurred during that series.
Clear the status register before beginning another command or sequence. The Read Array
command must be issued before data can be read from the memory array. Resetting the device also
clears the Status Register.
4.2 Program Mode
Programming is executed using a two-write cycle sequence. The Program Setup command (0x40)
is issued to the CUI followed by a second write which specifies the address and data to be
programmed. The WSM will execute a sequence of internally timed events to program preferred
bits of the addressed location, then verify the bits are sufficiently programmed. Programming the
memory results in specific bits within an address location being changed to a “0.” If users attempt
to program “1”s, the memory cell contents do not change and no error occurs.
The Status Register indicates programming status. While the program sequence executes, status bit
7 is “0.” The status register can be polled by toggling either CE# or OE#. While programming, the
only valid commands are Read Status Register, Program Suspend, and Program Resume.
When programming is complete, the program-status bits should be checked. If the programming
operation was unsuccessful, bit SR[4] of the Status Register is set to indicate a program failure. If
SR[3] is set, then V
PP
was not within acceptable limits, and the WSM did not execute the program
command. If SR[1] is set, a program operation was attempted on a locked block and the operation
was aborted.
The status register should be cleared before attempting the next operation. Any CUI instruction can
follow after programming is completed; however, to prevent inadvertent status-register reads, be
sure to reset the CUI to read-array mode.
4.2.1 12-Volt Production Programming
When V
PP
is between 1.65 V and 3.6 V, all program and erase current is drawn through the VCC
pin. Note that if V
PP
is driven by a logic signal, V
IH
min = 1.65 V. That is, V
PP
must remain above
1.65 V to perform in-system flash modifications. When V
PP
is connected to a 12 V power supply,
the device draws program and erase current directly from the VPP pin. This eliminates the need for
an external switching transistor to control V
PP
. Figure 7 on page 31 shows examples of how the
flash power supplies can be configured for various usage models.
