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PIC16CE625-04ISS

OTP 8-Bit CMOS MCU with EEPROM Data Memory

Microchip Technology 

3.0 ARCHITECTURAL OVERVIEW

The high performance of the PIC16CE62X family can

be attributed to a number of architectural features

commonly found in RISC microprocessors. To begin

with, the PIC16CE62X uses a Harvard architecture in

which program and data are accessed from separate

memories using separate buses. This improves

bandwidth over traditional von Neumann architecture

where program and data are fetched from the same

memory. Separating program and data memory further

allows instructions to be sized differently than 8-bit wide

data word. Instruction opcodes are 14-bits wide making

it possible to have all single word instructions. A 14-bit

wide program memory access bus fetches a 14-bit

instruction in a single cycle. A two-stage pipeline over-

laps fetch and execution of instructions. Consequently,

all instructions (35) execute in a single-cycle (200 ns @

20 MHz) except for program branches.

The table below lists program memory (EPROM), data

memory (RAM) and non-volatile memory (EEPROM)

for each PIC16CE62X device.

Device

PIC16CE623

PIC16CE624

Program

Memory

512x14

1Kx14

RAM EEPROM

Data

Data

Memory Memory

96x8

128x8

96x8

128x8

PIC16CE625

2Kx14 128x8 128x8

The PIC16CE62X can directly or indirectly address its

register files or data memory. All special function

registers including the program counter are mapped in

the data memory. The PIC16CE62X family has an

orthogonal (symmetrical) instruction set that makes it

possible to carry out any operation on any register

using any addressing mode. This symmetrical nature

and lack of ‘special optimal situations’ make program-

ming with the PIC16CE62X simple yet efficient. In addi-

tion, the learning curve is reduced significantly.

PIC16CE62X

The PIC16CE62X devices contain an 8-bit ALU and

working register. The ALU is a general purpose

arithmetic 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,

subtraction, shift and logical operations. Unless

otherwise mentioned, arithmetic operations are two's

complement in nature. In two-operand instructions,

typically one operand is the working register

(W register). The other operand is a file register or an

immediate constant. 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

respectively, bit in subtraction. See the SUBLW and

SUBWF instructions for examples.

A simplified block diagram is shown in Figure 3-1, with

a description of the device pins in Table 3-1.

© 1999 Microchip Technology Inc.

DS40182C-page 7

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