Microchip Technology AC244045 Data Sheet

 2010-2012 Microchip Technology Inc.

DS41440C-page 19

This family of devices contain an enhanced mid-range
8-bit CPU core. The CPU has 49 instructions. Interrupt
capability includes automatic context saving. The
hardware stack is 16 levels deep and has Overflow and
Underflow Reset capability. Direct, Indirect, and
Relative Addressing modes are available. Two File
Select Registers (FSRs) provide the ability to read
program and data memory.
• Automatic Interrupt Context Saving
• 16-level Stack with Overflow and Underflow
• File Select Registers
• Instruction Set

During interrupts, certain registers are automatically
saved in shadow registers and restored when returning
from the interrupt. This saves stack space and user
code. See 

for more information.

These devices have an external stack memory 15 bits
wide and 16 words deep. A Stack Overflow or
Underflow will set the appropriate bit (STKOVF or
STKUNF) in the PCON register, and if enabled will
cause a software Reset. See section 

 for more details.

There are two 16-bit File Select Registers (FSR). FSRs
can access all file registers and program memory,
which allows one Data Pointer for all memory. When an
FSR points to program memory, there is one additional
instruction cycle in instructions using INDF to allow the
data to be fetched. General purpose memory can now
also be addressed linearly, providing the ability to
access contiguous data larger than 80 bytes. There are
also new instructions to support the FSRs. See

 for more details.

There are 49 instructions for the enhanced mid-range
CPU to support the features of the CPU. See

 for more

details.