41594B datasheet(13/372 Pages) MICROCHIP

13 / 372 page

 2011-2012 Microchip Technology Inc.

Preliminary

DS41594B-page 13

PIC12LF1840T48A

2.0

ENHANCED MID-RANGE CPU

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

2.1

Automatic Interrupt Context

Saving

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 Section 8.5 “Automatic Context Saving”,

for more information.

2.2

16-Level Stack with Overflow and

Underflow

These devices have an external stack memory 15 bits

wide and 16 words deep. A Stack Overflow or Under-

flow will set the appropriate bit (STKOVF or STKUNF)

in the PCON register, and if enabled will cause a soft-

ware Reset. See Section 3.4 “Stack” for more details.

2.3

File Select Registers

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 1 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

Section 3.5 “Indirect Addressing” for more details.

2.4

Instruction Set

There are 49 instructions for the enhanced mid-range

CPU to support the features of the CPU. See

Section 30.0 “Instruction Set Summary” for more

details.

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