Information

PIC18F2220/2320/4220/4320
DS80396B-page 2 © 2009 Microchip Technology Inc.
2. Module: MSSP (All I
2
C™ and SPI Modes)
The Buffer Full flag bit (BF) of the SSPSTAT regis-
ter (SSPSTAT<0>) may be inadvertently cleared,
even when the SSPBUF register has not been
read. This will occur only when the following two
conditions occur simultaneously:
• The four Least Significant bits of the BSR
register are equal to 0Fh (BSR<3:0> = 1111)
and
• Any instruction that contains C9h in its 8 Least
Significant bits (i.e., register file addresses,
literal data, address offsets, etc.) is executed.
Work around
Identified work arounds will involve setting the
contents of BSR<3:0> to some value other than
0Fh.
In addition to those proposed below, other solutions
may exist.
1. When developing or modifying code, keep
these guidelines in mind:
• Assign 12-bit addresses to all variables.
This allows the assembler to know when
Access Banking can be used.
• Do not set the BSR to point to Bank 15
(BSR = 0Fh).
• Allow the assembler to manipulate the
Access bit present in most instructions.
Accessing the SFRs in Bank 15 will be done
through the Access Bank. Continue to use
the BSR to select all GPR Banks.
2. If accessing a part of Bank 15 is required and
the use of Access Banking is not possible,
consider using indirect addressing.
3. If pointing the BSR to Bank 15 is unavoidable,
review the absolute file listing. Verify that no
instructions contain C9h in the 8 Least Signifi-
cant bits while the BSR points to Bank 15
(BSR = 0Fh).
Date Codes that pertain to this issue:
All engineering and production devices.
3. Module: MSSP (SPI, Slave Mode)
In its current implementation, the SS (Slave
Select) control signal generated by an external
master processor may not be successfully recog-
nized by the PIC
®
microcontroller operating in
Slave Select mode (SSPM3:SSPM0 = 0100). In
particular, it has been observed that faster transi-
tions (those with shorter fall times) are more likely
to be missed than slower transitions.
Work around
Insert a series resistor between the source of the
SS
signal and the corresponding SS input line of
the microcontroller. The value of the resistor is
dependent on both the application system’s
characteristics and process variations between
microcontrollers. Experimentation and thorough
testing is encouraged.
This is a recommended solution; others may exist.
Date Codes that pertain to this issue:
All engineering and production devices.