RFPIC12C509AF datasheet(11/104 Pages) MICROCHIP

11 / 104 page

Preliminary

DS70031A-page 9

rfPIC12C509AG/509AF

3.0

ARCHITECTURAL OVERVIEW

The rfPIC12C509AG/509AF is a low-cost, high perfor-

mance, 8-bit, fully static, EPROM-based CMOS micro-

controller combined with a UHF ASK/FSK transmitter.

There are no internal electrical connections between

the PICmicro MCU and the transmitter.

Section 7 has a detailed description of UHF ASK/FSK

transmitter.

3.1

PICmicro Microcontroller Unit

The high performance of the rfPIC12C509AG/509AF

family can be attributed to a number of architectural

features commonly found in RISC microprocessors. To

begin with, the rfPIC12C509AG/509AF uses a Harvard

architecture in which program and data are accessed

on separate buses. This improves bandwidth over tra-

ditional von Neumann architecture where program and

data are fetched on the same bus. Separating program

and data memory further allows instructions to be sized

differently than the 8-bit wide data word. Instruction

opcodes are 12 bits wide making it possible to have all

single word instructions. A 12-bit wide program mem-

ory access bus fetches a 12-bit instruction in a single

cycle. A two-stage pipeline overlaps fetch and execu-

tion of instructions. Consequently, all instructions (33)

execute in a single cycle (1

µs @ 4MHz) except for pro-

gram branches.

The table below lists program memory (EPROM) and

data memory (RAM) for each device.

The rfPIC12C509AG/509AF can directly or indirectly

address its register files and data memory. All special

function registers including the program counter are

mapped in the data memory. The rfPIC12C509AG/

509AF has a highly orthogonal (symmetrical) instruc-

tion set that makes it possible to carry out any opera-

tion on any register using any addressing mode. This

symmetrical nature and lack of special optimal situa-

tions make programming with the rfPIC12C509AG/

509AF simple yet efficient. In addition, the learning

curve is reduced significantly.

The rfPIC12C509AG/509AF contains an 8-bit ALU and

working register. The ALU is a general purpose arith-

metic unit. It performs arithmetic and Boolean functions

between data in the working register and any register

file.

The ALU is 8 bits wide and capable of addition, subtrac-

tion, shift and logical operations. Unless otherwise

mentioned, arithmetic operations are two's comple-

ment in nature. In two-operand instructions, typically

one operand is the W (working) register. The other

operand is either a file register or an immediate con-

stant. In single operand instructions, the operand is

either the W register or a file register.

The W register is an 8-bit working register used for ALU

operations. It is not an addressable register.

Depending on the instruction executed, the ALU may

affect the values of the Carry (C), Digit Carry (DC), and

Zero (Z) bits in the STATUS register. The C and DC bits

operate as a borrow and digit borrow out bit, respec-

tively, in subtraction. See the SUBWF and ADDWF

instructions for examples.

3.2

UHF ASK/FSK Transmitter

The Transmitter is a fully integrated UHF ASK/FSK

transmitter consisting of crystal oscillator, phase-

locked loop (PLL), open-collector differential-output

Power Amplifier (PA), and mode control logic. External

components consist of bypass capacitors, crystal, and

PLL loop filter. There are no internal electrical connec-

tions between the PICmicro MCU and the transmitter.

The rfPIC12C509AG is capable of Amplitude Shift Key-

ing (ASK) modulation by turning the PA on and off. The

rfPIC12C509AF is capable of ASK or Frequency Shift

Keying (FSK) modulation by employing an internal FSK

switch to pull the transmitter crystal via a second load

capacitor.

The PICmicro MCU oscillator is independent from the

transmitter crystal oscillator. The transmit frequency is

fixed and set by an external reference crystal. Trans-

mit frequencies in the range of 310 to 480 MHz can be

selected. Output drive is an open-collector differential

amplifier. The differential output is well suited for loop

antennas. Output power is adjustable from +2 dBm to

-12 dBm in six discrete steps.

The rfPIC12C509AG/509AF are radio frequency (RF)

emitting devices. Wireless RF devices are governed by

a country’s regulating agency. For example, in the

United States it is the Federal Communications Com-

mittee (FCC) and in Europe it is the European Confer-

ence

Postal

and

Telecommunications

Administrations (CEPT). It is the responsibility of the

designer to ensure that their end product conforms to

rules and regulations of the country of use and/or sale.

Device

Memory

EPROM

Program

RAM

Data

Transmitter

rfPIC12C509AG

1024 x 12

ASK

rfPIC12C509AF

1024 x 12

ASK/FSK

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