PIC18F46K80-I/P Microchip Technology Inc., PIC18F46K80-I/P Datasheet - Page 112

• Manufacturer Part Number: PIC18F46K80-I/P
• Description: 40 PDIP .600IN TUBE, ECAN, 64KB FLASH, 4KB RAM, 16 MIPS, 12-BIT ADC, CTMU
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F46K80-I/P

• A/d Inputs: 11-Channel, 12-Bit
• Comparators: 2
• Cpu Speed: 16 MIPS
• Eeprom Memory: 1K Bytes
• Input Output: 35
• Interface: I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 44-pin PDIP
• Programmable Memory: 64K Bytes
• Ram Size: 3.6K Bytes
• Speed: 64 MHz
• Temperature Range: –40 to 125 °C
• Timers: 2-8-bit, 3-16-bit
• Voltage, Range: 1.8-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part

PIC18F66K80 FAMILY
6.3
The data memory in PIC18 devices is implemented as
static RAM. Each register in the data memory has a
12-bit address, allowing up to 4,096 bytes of data
memory. The memory space is divided into 16 banks
that contain 256 bytes each.
Figure 6-6
organization for the devices.
The data memory contains Special Function Registers
(SFRs) and General Purpose Registers (GPRs). The
SFRs are used for control and status of the controller
and peripheral functions, while GPRs are used for data
storage and scratchpad operations in the user’s
application. Any read of an unimplemented location will
read as ‘ 0 ’s.
The instruction set and architecture allow operations
across all banks. The entire data memory may be
accessed by Direct, Indirect or Indexed Addressing
modes. Addressing modes are discussed later in this
section.
To ensure that commonly used registers (select SFRs
and select GPRs) can be accessed in a single cycle,
PIC18 devices implement an Access Bank. This is a
256-byte memory space that provides fast access to
select SFRs and the lower portion of GPR Bank 0 with-
out using the Bank Select Register. For details on the
Access RAM, see
DS39977C-page 112
Note:
Data Memory Organization
The operation of some aspects of data
memory are changed when the PIC18
extended instruction set is enabled. See
Section 6.6 “Data Memory and the
Extended Instruction Set”
information.
and
Figure 6-7
Section 6.3.2 “Access Bank”
show the data memory
for more
.
Preliminary
6.3.1
Large areas of data memory require an efficient
addressing scheme to make rapid access to any
address possible. Ideally, this means that an entire
address does not need to be provided for each read or
write operation. For PIC18 devices, this is accom-
plished with a RAM banking scheme. This divides the
memory space into 16 contiguous banks of 256 bytes.
Depending on the instruction, each location can be
addressed directly by its full 12-bit address, or an
eight-bit, low-order address and a four-bit Bank Pointer.
Most instructions in the PIC18 instruction set make use
of the Bank Pointer, known as the Bank Select Register
(BSR). This SFR holds the four Most Significant bits of
a location’s address. The instruction itself includes the
eight Least Significant bits. Only the four lower bits of
the BSR are implemented (BSR<3:0>). The upper four
bits are unused and always read as ‘ 0 ’, and cannot be
written to. The BSR can be loaded directly by using the
MOVLB instruction.
The value of the BSR indicates the bank in data
memory. The eight bits in the instruction show the loca-
tion in the bank and can be thought of as an offset from
the bank’s lower boundary. The relationship between
the BSR’s value and the bank division in data memory
is shown in
Since up to 16 registers may share the same low-order
address, the user must always be careful to ensure that
the proper bank is selected before performing a data
read or write. For example, writing what should be
program data to an eight-bit address of F9h while the
BSR is 0Fh, will end up resetting the program counter.
While any bank can be selected, only those banks that
are actually implemented can be read or written to.
Writes to unimplemented banks are ignored, while
reads from unimplemented banks will return ‘ 0 ’s. Even
so, the STATUS register will still be affected as if the
operation was successful. The data memory map in
Figure 6-6
In the core PIC18 instruction set, only the MOVFF
instruction fully specifies the 12-bit address of the
source and target registers. When this instruction
executes, it ignores the BSR completely. All other
instructions include only the low-order address as an
operand and must use either the BSR or the Access
Bank to locate their target registers.
indicates which banks are implemented.
BANK SELECT REGISTER
Figure
6-7.
 2011 Microchip Technology Inc.