HCS360

© 1996 Microchip Technology Inc.

Preliminary

DS40152C-page 13

6.0

PROGRAMMING THE HCS360

When using the HCS360 in a system, the user will have

to program some parameters into the device including

the serial number and the secret key before it can be

used. The programming

allows the user to input all

192 bits in a serial data stream, which are then stored

internally in EEPROM. Programming will be initiated by

forcing the PWM line high, after the S3 line has been

held high for the appropriate length of time. S0 and S1

should be held low during the entire program cycle

(Table 6-1 and Figure 6-1). The device can then be pro-

grammed by clocking in 16 bits at a time, followed by

the word’s complement using S3 or S2 as the clock line

and PWM as the data in line. After each 16-bit word is

loaded, a programming delay is required for the internal

program cycle to complete. The acknowledge can read

word and its complement have been downloaded, an

automatic bulk write is performed. This delay can take

up to Twc. At the end of the programming cycle, the

device can be verified (Figure 6-2) by reading back the

EEPROM. Reading is done by clocking the S3 line and

reading the data bits on PWM. For security reasons, it

is not possible to execute a verify function without first

programming the EEPROM. A verify operation can

only be done once, immediately following the pro-

gram cycle.

FIGURE 6-1:

PROGRAMMING WAVEFORMS

FIGURE 6-2:

VERIFY WAVEFORMS

TABLE 6-1

PROGRAMMING/VERIFY TIMING REQUIREMENTS

± 10%

25

° C ± 5 °C

Parameter

Symbol

Min.

Max.

Units

Program mode setup time

0

4.0

ms

Hold time 1

9.0

—

ms

Program cycle time

—

30

ms

Clock low time

25

—

µs

Clock high time

25

—

µs

Data setup time

0

—

µs

Data hold time

18

—

µs

Data out valid time

—

24

µs

PWM

Enter Program

Mode

(Data)

(Clock)

Bit 0

Bit 1

Bit 2

Bit 3

Bit 14 Bit 15

Bit 16 Bit 17

Repeat 12 times for each word

S2/S3

Data for Word 0 (KEY_0)

Data for Word 1

Bit 0

Bit 1

Bit 2

Bit 3

Bit 14 Bit 15

Note 1: Unused button inputs to be held to ground during the entire programming sequence.

Acknowledge

PWM

(Clock)

(Data)

Note: If a Verify operation is to be done, then it must immediately follow the Program cycle.

End of

Programming Cycle

Begin Verify Cycle Here

Bit 1 Bit 2

Bit 3

Bit 15

Bit 14

Bit 16 Bit 17

Bit190 Bit191

Data in Word 0

S2/S3

Bit 0

Bit191

Bit190