IS27HC010
FUNCTIONAL DESCRIPTION
Erasing the IS27HC010
In order to clear all locations of their programmed contents,
it is necessary to expose the IS27HC010 to an ultraviolet
light source. A dosage of 30W - sec/cm
2
is required to
completely erase the IS27HC010. This dosage can be
obtained by exposure to an ultraviolet lamp-wavelength of
2537 Angstroms (Å)—with intensity of 12,000
µW/cm
2
for
30 to 40 minutes. The IS27HC010 should be directly under
and about one inch from the source and all filters should be
removed from the UV light source prior to erasure.
It is important to note that the IS27HC010, and similar
devices, will erase with light sources having wavelengths
shorter than 4000Å. The exposure to fluorescent light and
sunlight will eventually erase the IS27HC010 and expo-
sure to them should be prevented to realize maximum
system reliability. If used in such an environment, the
package window should be covered by an opaque label or
substance.
Programming the IS27HC010
Upon delivery, or after each erasure, the IS27HC010 has
1,048,576 bits in the "ONE", or HIGH state. "ZEROs" are
loaded into the IS27HC010 through the procedure of
programming.
The programming mode is entered when 12.75
±
0.25V is
applied to the V
PP
pin, V
CC
= 6.25V,
CE
and
PGM
is at V
IL
,
and
OE
is at V
IH
. For programming, the data to be pro-
grammed is applied eight bits in parallel to the data output
pins.
The write programming algorithm reduces programming
time by using 100
µs
programming pulses followed by a
byte verification to determine whether the byte has been
successfully programmed. If the data does not verify, an
additional pulse is applied for a maximum of 25 pulses.
This process is repeated while sequencing through each
address of the EPROM.
The write programming algorithm programs and verifies at
V
CC
= 6.25V and V
PP
= 12.75V. After the final address is
completed, all byte are compared to the original data with
V
CC
= 5.25V.
Program Inhibit
Programming of multiple IS27HC010s in parallel with
different data is also easily accomplished. Except for
CE
,
all like inputs of the parallel IS27HC010 may be common.
A TTL low-level program pulse applied to an IS27HC010
CE
input with V
PP
= 12.75
±
0.25V,
PGM
LOW and
OE
HIGH will program that IS27HC010. A high-level
CE
input
inhibits the other IS27HC010 from being programmed.
ISSI
®
Program Verify
A verify should be performed on the programmed bits to
determine that they were correctly programmed. The
verify should be performed with
OE
and
CE
at V
IL
,
PGM
at
V
IH
, and V
PP
between 12.5V and 13.0V.
Auto Select Mode
The auto select mode allows the reading out of a binary
code from an EPROM that will identify its manufacturer
and type. This mode is intended for use by programming
equipment for the purpose of automatically matching the
device to be programmed with its corresponding program-
ming algorithm. This mode is functional in the 25°C
±
5°C
ambient temperature range that is required when pro-
gramming the IS27HC010.
To activate this mode, the programming equipment must
force 12.0
±
0.5V on address line A9 of the IS27HC010.
Two identifier bytes may then be sequenced from the
device outputs by toggling address line A0 from V
IL
to V
IH
.
All other address lines must be held at V
IL
during auto
select mode.
Byte 0 (A0 = V
IL
) represents the manufacturer code, and
byte 1 (A0 = V
IH
), the device identifier code. For the
IS27HC010, these two identifier bytes are given in the
Mode Select table. All identifiers manufacturer and device
codes will possess odd parity, with the MSB (DQ7) defined
as the parity bit.
Read Mode
The IS27HC010 has two control functions, both of which
must be logically satisfied in order to obtain data at the
outputs. Chip Enable (
CE
) is the power control and should
be used for device selection. Assuming that addresses are
stable, address access time (t
ACC
) is equal to the delay
from
CE
to output (t
CE
). Output Enable (
OE
) is the output
control and should be used to get data to the output pins,
independent of device selection. Data is available at the
outputs t
OE
after the falling edge of
OE
assuming that
CE
has been LOW and addresses have been stable for at
least t
ACC
– t
OE
.
Standby Mode
The IS27HC010 has a standby mode which reduces the
maximum V
CC
active current. It is placed in standby mode
when
CE
is at V
IH
. The amount of current drawn in standby
mode depends on the frequency and the number of
address pins switching. The IS27HC010 is specified with
50% of the address lines toggling at 10 MHz. A reduction
of the frequency or quantity of address lines toggling will
significantly reduce the actual standby current.
Integrated Silicon Solution, Inc.
EP009-1F
07/18/97
3
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
