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2004 Microchip Technology Inc. DS00915A-page 1
AN915
INTRODUCTION
Microchip Technology recently introduced a new family
of Microwire serial EEPROMs with smaller packaging,
faster write times, and faster bus speeds. In addition to
this migration document, we recommend that you
review the data sheets for each device to see how
these changes may apply to your system requirements.
This document is intended to assist customers with
migrating to the latest Microchip Technology Microwire
EEPROMs from older versions of our products.
This document addresses migration of 93XX46,
93XX56, and 93XX66 devices with a selectable ORG
pin to 93XX46C, 93XX56C, and 93XX66C compo-
nents, respectively. There are six topics addressed
throughout this text:
• Bus Speed Compatibility
• Write Cycle Time
• Write Cycle Initiation
• Ready/Busy
Operations
• Noise Immunity
• New Packaging Options
FIGURE 1: RECOMMENDED
MIGRATION PATHS
BUS SPEED COMPATIBILITY
When the power supply applied to the chip is below 4.5
Volts, the new 93LCX6C devices can run up to 2 MHz
as opposed to the 1 MHz bus speed of 93LCX6
devices.
WRITE CYCLE TIME
Write cycle time is also a key specification for system
designers. Many of these specifications remained the
same for the recommended migration paths, and some
improved. Differences between the families are noted
in Table 1.
TABLE 1: WRITE CYCLE TIME
DIFFERENCES
INITIATING WRITE CYCLES
Depending on the migration path taken, write cycle
initiation may have also changed. Almost all of the
methodologies remained the same. However, those
that did change were limited to 93CX6 devices when
migrating to the 93CX6C Family. For older devices,
93CX6, the write cycle initiated after the last data bit.
On the newer devices, the write cycle now initiates on
the rising edge of the last data bit clock. The latest
waveform is shown in Figure 2 and the timing charac-
teristics for each symbol can be found in the respective
data sheets. This change does not effect 93AAX6 or
93LCX6 devices.
Author: Ken Dietz
Microchip Technology Inc.
93AAX6
93LCX6
93CX6
93AAX6C
93LCX6C
93CX6C
X = 4, 5 or 6
1 Kbit 93XX46C
2 Kbit 93X56C
4 Kbit 93XX66C
Old Part
Number
Old Spec.
(Maximum)
New Part
Number
New Spec.
(Maximum)
93CX6 10 ms 93CX6C 2 ms
93AAX6 10 ms 93AAX6C 6 ms
93LCX6 10 ms 93LCX6C 6 ms
X = 4, 5 or 6
1K, 2K and 4K Microwire EEPROM Migration
