GR4x to GR64 Migration Guide
3.2.5
Real Time Clock Voltage
Pin
GR64
GR4x
Functional Difference
25 VRTC VRTC
Voltage
range
The GR4x and GR64 Real Time Clock (RTC) can be powered by a backup device when
the Wireless CPU®s are not powered. When the Wireless CPU® is powered the backup
component (a battery cell or capacitor) can be re-charged. The mechanics of VRTC is
similar for both devices, but the charging voltage and the backup voltage discharge
limit is marginally different, with the GR64 being a narrower guaranteed range.
Change Impact: In most applications, which require backup periods less than a few
weeks, this will not present a problem.
3.2.6
A to D Converter
Pin
GR64
GR4x
Functional Difference
22
GPIO2
ADC5* Does not exist in GR64
13 ADIN4 ADC4
26 ADIN1 ADC1
Migration Guide
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27 ADIN2 ADC2
Input resolution & range
28 ADIN3 ADC3
The GR64 has a 10-bit ADC, compared with its predecessor product which only
offered 8-bit resolution. The input voltage range is slightly narrow in the GR64.
Change Impact: Some additional calibration to adjust the A to D conversion scaling is
all that will be required.
3.2.7
Regulated Voltage Reference
Pin
GR64
GR4x
Functional Difference
34
VREF
VIO
Integrated level shifters now provided
The GR4x series provided VIO as an indication of power-on to the host, and as a
current limited supply for external applications, mostly to be used as a reference for
level shifters.
The Legacy variant GR64 provides similar functionality, except its use as a level-
shifter reference voltage is superseded in the most part by the inclusion of integrated
level shifters in the modem. The VREF output is 2.8V. This 2.8V output becomes
high impedance at power down compared to grounded in GR4x series.
GR4x to GR64
Page 18 of 28
