Output Disable Mode
With the /OE input at a logic high level (V
IH
), output
from the device is disabled. This will cause the
output pins to be in a high impedance state. It is
shown in Table 1 that /CE = V
IL
and /WE = V
IH
for
Output Disable. This is to differentiate Output Dis-
able mode from Write mode and to prevent
inadvertant writes during Output Disable.
mode that disables both Programming and Erase
operation to protected sectors. In this device there
are 8 sectors of 64K bytes each. The sector protect
feature is enabled using programming equipment
at the user’s site. The device is shipped from
Hyundai’s factory with all sectors unprotected.
To activate the Sector Protect mode, the user
must force V
ID
on address pin A9 and control pin /
OE. The sector addresses (A18, A17 and A16)
should be set to the sector to be protected (see
Table 3 for the sector address for each of the eight
individual sectors). Programming of the protec-
tion circuitry starts on the falling edge of /WE pulse
and is terminated with the rising edge of
/WE. Sector addresses must be held fixed during
the /WE pulse.
To verify programming of the protection circuitry,
the programming equipment must force V
ID
on the
address pin A9 with /CE and /OE at V
IL
and
/WE at V
IH
. As shown in Table 2, scanning the
sector addresses (A18, A17 and A16) while (A6,
A1 and A0) = (0, 1, 0) will produce a 01H code at
the device output pins for a protected sector. In
the Verify Sector Protect mode, the device will read
00H for an unprotected sector. In this mode, the
lower order addresses, except for A0, A1 and A6,
are don’t care. Address locations with A1 = V
IL
are
reserved for electronic ID manufacturer and de-
vice codes. It is also possible to determine if a
sector is protected in-system by writing the Elec-
tronic ID command (described in the Electronic
ID command section below).
Write Mode
Device programming and erase are accomplished
via the command register. The contents of the reg-
ister serve as inputs to the internal state machine.
Outputs of the state machine dictate the function
of the device.
The command register itself does not occupy any
addressable memory locations. The register is a
latch used to store the commands along with the
addresses and data information needed to execute
the command. The command register is written
by bringing /WE to V
IL
, while /CE is at V
IL
and /OE
is at V
IH
. Addresses are latched on the falling edge
of /WE or /CE, whichever happens later, while data
is latched on the rising edge of /WE or /CE, which-
ever happens first. Standard microprocessor
write timings are used. Refer to AC Characteris-
tics for Programming/Erase and their respective
Timing Waveforms for specific timing parameters.
Enable Sector Protect and Verify
Sector Protect Modes
The HY29F040A has a hardware Sector Protect
6
HY29F040A
HYNIX [ HYNIX SEMICONDUCTOR ]
