Datasheet

 2010 Microchip Technology Inc. DS39770C-page 401
PIC18F85J90 FAMILY
B.1 Power Requirement Differences
The most significant difference between the
PIC18F85J90 and PIC18F8490 device families is the
power requirements. PIC18F85J90 family devices are
designed on a smaller process. This results in lower
maximum voltage and higher leakage current.
The operating voltage range for PIC18F85J90 devices
is 2.0V to 3.6V. In addition, these devices have split
power requirements: one for the core logic and one for
the I/O. One of the V
DD pins is separated for the core
logic supply (V
DDCORE). This pin has specific voltage
and capacitor requirements as described in
Section 26.0 “Electrical Characteristics”.
B.2 Oscillator Differences
PIC18F8490 and PIC18F85J90 family devices share a
similar range of oscillator options. The major difference
is that PIC18F85J90 family devices support a smaller
number of primary (external) oscillator options, namely
HS and EC Oscillator modes.
While both device families have an internal PLL that
can be used with the primary oscillators, the PLL for the
PIC18F85J90 family is not enabled as a device
configuration option. Instead, it must be enabled in
software.
The clocking differences should be considered when
making a conversion between the PIC18F8490 and
PIC18F85J90 device families.
B.3 LCD Module
When converting an LCD application between the
PIC18F85J90 and the PIC18F8490 families, the
following things must be considered:
• Available Segments: The module for
PIC18F65J90 devices supports 33 segments, as
opposed to 32 segments in PIC18F6490 devices.
(The 80-pin devices of both families support
48 segments. All devices support 4 commons.)
• Bias Generation: The PIC18F85J90 version of
the module also incorporates its own independent
voltage regulator, which supports 4 circuit configu-
rations for bias generation, voltage boost to
support displays that operate above device V
DD
and software contrast control.
• Additional LCD Function Pins: The
PIC18F85J90 family of devices adds 3 additional
LCD function pins in comparison to the
PIC18F8490 family. The additional pins are
associated with LCD bias generation:
- LCDBIAS0 (RG0)
-V
LCAP1 (RG2)
-V
LCPA2 (RG3)
• Segment Assignments: Eight of the LCD
segment functions have been relocated to differ-
ent I/O pins than in PIC18F8490 devices. These
segments are listed in Table B-2.
• Other Considerations: In all LCD applications,
the connections of PIC18F85J90 devices to
external components for LCD bias generation are
different than PIC18F8490 devices. The addition
of the LCDBIAS0 output requires that this pin be
included in bias component configurations. A
more complete discussion is provided in
Section 16.3 “LCD Bias Generation”.
The simultaneous use of the external Timer1
oscillator and Segment 32 is not allowed in
PIC18F85J90 devices, since these functions are
shared on the same pin.
TABLE B-2: ASSIGNMENTS OF MOVED
LCD SEGMENTS
LCD Segment PIC18F8490 PIC18F85J90
SEG16 RA2 RC4
SEG17 RA3 RC3
SEG18 RF0 RA1
SEG27 RG3 RC6
SEG28 RG2 RC7
SEG29 RG0 RB5
SEG30 RG0 RB0
SEG32 RJ0 RC1
Note: Refer to the pinout diagrams for pin
locations of I/O ports.