Product Data Sheets
ISD2500 Series
1–88
-1
ISD1000A COMPATIBILITY
The ISD2500 Series of devices is designed to pro-
vide upward compatibility with the ISD1000A
family. When designing with the ISD2500 Series,
the
following
differences
should
be
noted.
Addressing
The ISD2560/75/90/120 devices have 480K stor-
age cells designed to provide 60 seconds of
storage at a sampling rate of 8.0 KHz. This is
approximately four times the storage of the
ISD1000A family. To enable the same addressing
resolution, two additional address pins have been
added. The address space of each device is divis-
ible into 300 increments with valid addressing from
00 to 13F Hex. Some higher addresses are
mapped into the Operational Modes. All other
addresses are invalid.
The ISD2532/40/48/64 devices have 256K storage
cells designed to provide 32 seconds of storage at
a sampling rate of 8.0 KHz. This is twice the
amount of storage of the ISD1000A family. To
enable the same addressing resolution, one addi-
tional address pin has been added. The address
space of each device is divisable into 320 incre-
ments with valid addressing from 00 to 13F Hex.
Overflow
The ISD1000A Series combined two functions on
the EOM pin: end-of-message indication and over-
flow. The ISD2500 separates these two functions.
Pin 25 (PDIP package) remains as EOM, but out-
puts only the EOM signal indication. Pin 22 (PDIP
package) becomes OVF and pulses LOW only
when the device reaches its end of memory, or is
“full.” This change allows easy message cueing
and addressability across device boundaries. This
also means that the M2 operational mode found in
the ISD1000A family is not implemented in the
ISD2500 Series.
Push-Button Mode
The ISD2500 Series includes an additional Opera-
tional Mode called Push-Button mode. This
provides an alternative interface to the Record and
Playback functions of the part. The CE and PD
pins become redefined as edge-activated “push-
buttons.” A pulse on CE initiates a cycle, and if
triggered again, pauses the current cycle without
resetting the address pointer (i.e., a Start or Pause
function). PD stops any current cycle and resets
the address pointer to the beginning of the mes-
sage space (i.e., a Stop and Reset function).
Additionally, the EOM pin functions as an active-
HIGH run indicator, and can be used to drive an
LED indicating a Record or Playback operation is
in progress. Devices in the Push-Button mode can-
not be cascaded.
Looping Mode
The ISD2500 Series can loop with a message that
completely fills the memory space.
NOTE
Additional descriptions of ISD2500 device
functionality and application examples are
provided in the ISD Application Notes and
Design Manual in this book.
* Advance information: ISD2532/40/48/64 devices.
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