A PC-Based Development Programmer for the PIC16C84.pdf

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AN589

After entering programming mode, RB7 is used to

serially enter programming modes and data into the

part. A high to low transition on RB6, the clock input,

qualiﬁes each bit of the data applied on RB7. Please

refer to the PIC16C84 Programming Speciﬁcation

(DS30189) for details on the ﬁgures. The serial com-

mand-data format is speciﬁed in Figure 1.2.1.3 of the

Microchip PIC16C84 Programming Speciﬁcation

(DS30189). The ﬁrst 6 bits form the command ﬁeld, and

the last 16 bits form the data ﬁeld. Notice that the data

ﬁeld is composed of one zero starting bit, 14 actual

data bits, and one zero stop bit. The increment address

command, shown in Figure 1.2.1.5 (PIC16C84 Pro-

gramming Speciﬁcation, DS30189), is comprised of

only the command ﬁeld. Table 1.2.1.1 (see DS30189)

summarizes the available commands and command

codes for serial programming mode.

Read mode is similar to programming mode with the

exception that the data direction of RB7 is reversed

after receiving the 6-bit command to allow the

requested data to be returned to the programmer.

Figure 1.2.1.4 (see DS30189) shows this sequence

which starts by shifting the 6-bit command into the part.

After the read command is issued, the programmer

tri-states its buffer to allow the part to serially shift its

internal data back to the programmer. The rising edge

of RB6, (the clock input), controls the data ﬂow by

sequentially shifting previously programmed or data

bits from the part. The programmer qualiﬁes this data

on the falling edge of RB6. Notice that 16 clock cycles

are necessary to shift out 14 data bits.

Accidental in-circuit reprogramming is prevented during

normal operation by the MCLR voltage which should

never exceed the maximum circuit supply voltage of

6 VDC and the logic levels of port bits RB7 and RB6.

After program/veriﬁcation the MCLR pin is brought low

to reset the target microcontroller and then electrically

released. The target circuit is then free to activate the

MCLR signal. In the event MCLR is not forced by the

target circuit, R4 (a 2 k

Ω

pull-up resistor in the

programmer) provides a high logic level on the target

microcontroller which enables execution of its program

independent of the programmer connection. Provisions

should be made to prevent the target circuit from

resetting the target microcontroller with MCLR or

affecting the RB7 and RB6 pins during the

programming process. In most cases this can be done

without jumpers.

A PC-Based Development Programmer for the PIC16C84

Robert Spur

Analog Design Specialist, Inc.

INTRODUCTION

This application note describes the construction of a

low cost serial programmer which uses a PC with a par-

allel (Centronix printer) port to control a PIC16C84.

This programmer has the capability of programming a

PIC16C84 microcontroller, and reading back internal

data without removing the device from the target circuit.

This feature is very useful in applications where

changes in program code or program constants are

necessary to compensate for other system features.

For example, an embedded control system may have to

compensate for variances in a mechanical actuator’s

performance or loading. The basic program can be pro-

grammed and tested during design phase. The ﬁnal

program and control constants can be easily added

later in the production phase without removing the

microcontroller from the circuit.

Automatic software and performance upgrades can

also be implemented in-system. Upon receiving new

system software via disk or modem, a control

processor with the included programming code could

perform

in-circuit

reprogramming

other

microcontrollers in the system.

This programmer can load program code, part

conﬁguration, and EEPROM data into the PIC16C84.

In read back mode, it can verify all data entries.

PROGRAMMING DESCRIPTION

The PIC16C84 microcontroller is placed into program-

ming mode by forcing a low logic level on RB7 (pin 13)

and RB6 (pin 12) while MCLR (pin 4) is ﬁrst brought low

to reset the part, and then brought to the program/verify

voltage of 12 to 14V. The MCLR pin remains at the pro-

gram/verify voltage for the remainder of the program-

ming or veriﬁcation.

1997 Microchip Technology Inc.

DS00589A-page 1

AN589

DETAILED CIRCUIT DESCRIPTION

A logic high on PC parallel interface latch bit D4 turns

on Q3 causing the MCLR pin to go low which places

the target part in reset mode. The reset condition is

then removed and the program/verify voltage is applied

by placing a logic high on D3 and a logic low on D4

which turns off Q3 and turns on Q2 and Q1. Circuit

protection of Q1 and Q3 is obtained from connecting

the emitter of Q2 to latch bit D4 which prevents a

simultaneous reset and program/verify voltage mode.

Q2, a 2N3904, has a reverse emitter base breakdown

voltage of 6V which will not be exceeded when 5V logic

is used on the parallel interface.

Resistors R1, R2, R3, and diode D1 provide a logic

level interface to the analog circuitry. R4 provides a

MCLR (master clear) pull-up function during target cir-

cuit run mode. The programming voltage is supplied

and adjusted by an external lab supply. This supply

should have a current limit in the 100 mA range. 5V for

U2 (LS244) is locally regulated from programming

supply voltage by U1. R5 (750

Ω

resistor) is connected

to the regulator output to insure proper 5V regulation

when the 13.5V programming voltage is applied

through the pull-up resistor R4.

Data and clock are connected to the part via tri-state

buffer, U2. PC parallel port interface bit D0 is used for

data and port bit D1 is used for clock. During

programming mode both clock and data buffers are

enabled by port bits D2 and D5. During read mode, the

data buffer is tri-stated via D2 and the printer data

acknowledge signal line is used to receive veriﬁcation

data from the part.

After program/veriﬁcation mode both the data and

clock lines are tri-stated via D2 and D5, allowing these

lines to be used by the target circuit. This allows the

programmer to remain physically, but not electrically

connected to the target system.

An optional 5V line was included in the 3-foot

programming interconnect cable for convenience.

Short interconnection leads and good grounding are

always good construction practice.

To meet the programming/veriﬁcation speciﬁcation, the

target part’s supply voltage should ﬁrst be set to the

maximum speciﬁed supply voltage and a program/data

read back should then be performed. This process is

then repeated at the lowest speciﬁed supply voltage.

FIGURE 1:

PROGRAMER SCHEMATIC

(13.5V)

µF

35V

LM340-5

2N3906

2N3904

1N4148

LS244 (pin 10)

2N3904

GND (pin 5)

PIC16C84

INTERFACE

750

LS244 (pin 20)

+5 VDC

µF

10V

MCLR (pin 4)

PC PARALLEL D4

INTERFACE

GND

18, 25

74LS244

DATA (RB7, pin 13)

ACK

74LS244

Resistors: 1/4 watt, 5%

CLOCK (RB6, pin 12)

BUSY

DS00589A-page 2

1997 Microchip Technology Inc.

AN589

SOFTWARE DESCRIPTION

The listed code provides a hardware-software interface

to a standard PC parallel (Centronix) interface port. The

code can be adapted to a microprocessor parallel inter-

face port by substituting an output command for the

“

biosprint

” command.

Control software can transfer the PIC16C84 program,

conﬁguration bits, and EEPROM data from a standard

PROM interface ﬁle into the target system by reading

the ﬁle and calling the function in Example 1 using the

appropriate command name in the deﬁnition table, and

the data to be programmed. The command names are

repeated here for reference.

LOAD_CONFIG

LOAD_DATA

READ_DATA

INC_ADDR

Sets PIC16C84 data pointer to

conﬁguration.

Loads, but does not program,

data.

Reads data at current pointer

location.

Increments

pointer.

PIC16C84

data

BEGIN_PROG

PARALLEL_MODE

LOAD_DATA_DM

READ_DATA_DM

Programs data at current data

pointer location.

Puts PIC16C84 into parallel

mode (not used).

Loads EEPROM data.

Reads EEPROM data.

Function “

int ser_pic16c84

(<command>,<data [or

0]>) is called to perform command. Function returns

internal data after read commands.

Do not forget to initiate the programming mode before

programming, increment the addresses after each byte

is programmed, and put the programmer in run mode

after programming.

Analog Design Specialist, Inc.

P.O. Box 26-0846

Littleton, CO 80126

EXAMPLE 1:

PUT TARGET SYSTEM INTO PROGRAM MODE

.. program code..

ser_pic16c84(PROGRAM_MODE,0);

.. program code..

EXAMPLE 2:

READ DATA FROM THE TARGET SYSTEM

.. program code..

data = ser_pic16c84(READ_DATA,0); // read data

// transfers data from target part to variable “data”

.. more program code..

EXAMPLE 3:

PROGRAM DATA INTO THE TARGET SYSTEM

.. program code..

ser_pic16c84(LOAD_DATA,data);// load data into target

ser_pic16c84(BEGIN_PROG,0);// program loaded data

ser_pic16c84(INC_ADDR,0);// increment to next address

// transfers data from program variable “data” to target part

.. more program code..

EXAMPLE 4:

PUT TARGET SYSTEM INTO RUN MODE

.. program code..

ser_pic16c84(RUN,0);

.. program code..

1997 Microchip Technology Inc.

DS00589A-page 3

AN589

//************************** FIGURE #2 ********************************

//**

SERIAL PROGRAMMING ROUTINE FOR THE PIC16C84 MICROCONTROLLER

//**

Analog Design Specialists

//**

//*********************************************************************

//FUNCTION PROTOTYPE: int ser_pic16c84(int cmd, int data)

// cmd: LOAD_CONFIG

-> part configuration bits

LOAD_DATA

-> program data, write

READ_DATA

-> program data, read

INC_ADDR

-> increment to the next address (routine does not auto increment)

BEGIN_PROG

-> program a previously loaded program code or data

LOAD_DATA_DM -> load EEPROM data regesters (BEGIN_PROG must follow)

READ_DATA_DM -> read EEPROM data

// data: 1) 14 bits of program data or

2) 8 bits of EEPROM data (least significant 8 bits of int)

// Additional programmer commands (not part of PIC16C84 programming codes)

// cmd: RESET

-> provides 1 ms reset pulse to target system

PROGRAM_MODE -> initializes PIC16C84 for programming

RUN

-> disconnects programmer from target system

// function returns:1) 14 or 8 bits read back data for read commands

2) zero

for write data commands

3) PIC_PROG_EROR = -1 for programming function errors

4) PROGMR_ERROR = -2 for programmer function errors

#include <bios.h>

#define

LOAD_CONFIG

LOAD_DATA

READ_DATA

INC_ADDR

BEGIN_PROG

PARALLEL_MODE 10

LOAD_DATA_DM

READ_DATA_DM

MAX_PIC_CMD

// not used

// division between pic16c84 and programmer commands

// external reset command, not needed for programming

// initialize program mode

// electrically disconnect programmer

#define RESET

#define PROGRAM_MODE

#define RUN

#define PIC_PROG_EROR -1

#define PROGMR_ERROR -2

#define PTR

// use device #0

// parallel port bits

d0: data output to part to be programmed

d1: programming clock

d2: data dirrection, 0= enable tri state buf -> send data to part

d3: Vpp control 1= turn on Vpp

d4: ~MCLR =0, 1 = reset device with MCLR line

d5: clock line tri state control, 0 = enable clock line

int ser_pic16c84(int cmd, int data)

{

int i, s_cmd;

// custom interface for pic16c84

DS00589A-page 4

1997 Microchip Technology Inc.

AN589

if(cmd <=MAX_PIC_CMD)

{

biosprint(0,8,PTR);

s_cmd = cmd;

for (i=0;i<6;i++)

{

biosprint(0,(s_cmd&0x1) +2+8,PTR);

biosprint(0,(s_cmd&0x1)

+8,PTR);

s_cmd >>=1;

}

if((cmd ==INC_ADDR)||(cmd ==PARALLEL_MODE)

return 0;

else if(cmd ==BEGIN_PROG)

{

delay(10);

return 0;

}

// all programming modes

// set bits 001000, output mode, clock & data low

// retain command “cmd”

// output 6 bits of command

// set bits 001010, clock hi

// set bits 001000, clock low

// command only, no data cycle

// program command only, no data cycle

// 10 ms PIC programming time

else if((cmd ==LOAD_DATA)||(cmd ==LOAD_DATA_DM)||(cmd ==LOAD_CONFIG)) // output 14 bits

for (i=200;i;i—) ;

// delay between command & data

biosprint(0,2+8,PTR);

// set bits 001010, clock hi; leading bit

biosprint(0, 8,PTR);

// set bits 001000, clock low

for (i=0;i<14;i++)

{

biosprint(0,(data&0x1) +2+8,PTR);

biosprint(0,(data&0x1)

+8,PTR);

data >>=1;

}

biosprint(0,2+8,PTR);

// *****************

biosprint(0,

return 0;

}

else if((cmd ==READ_DATA)||(cmd ==READ_DATA_DM)) //read 14 bits from part, lsb first

{

biosprint(0, 4+8,PTR);

// set bits 001100, clock low, tri state data buffer

for (i=200;i;i—) ;

// delay between command & data

biosprint(0,2+4+8,PTR);

// set bits 001110, clock hi, leading bit

biosprint(0, 4+8,PTR);

// set bits 001100, clock low

data =0;

for (i=0;i<14;i++)

Analog Design Specialists

// 14 data bits, lsb first

// set bits 001010,

// set bits 001000,

clock hi

clock low

// set bits 001010, clock hi; trailing bit

******************

// set bits 001000, clock low

8,PTR);

// input 14 bits of data, lsb first

{

data >>=1;

// shift data for next input bit

biosprint(0,2+4+8,PTR);

// set bits 001110, clock hi

biosprint(0, 4+8,PTR);

// set bits 001100, clock low

if(!(biosprint(2,0,0)&0x40)) data += 0x2000; //use printer acknowledge line for input,

//data lsb first

}

biosprint(0,2+4+8,PTR);

// set bits 001110, clock hi, trailing bit

biosprint(0, 4+8,PTR);

// set bits 001100, clock low

return data;

}

else return PIC_PROG_EROR;

}

else if(cmd == RESET)

// programmer error

// reset device

1997 Microchip Technology Inc.

DS00589A-page 5

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