 2001 Microchip Technology Inc.

DS40152D-page 15

HCS360

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 should

be held low during the entire program cycle. The S1

line on the HCS360 part needs to be set or cleared

depending on the LS bit of the memory map (Key 0)

before the key is clocked in to the HCS360. S1 must

remain at this level for the duration of the programming

cycle. The device can then be programmed 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 com-

plete. The acknowledge can read back after the pro-

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 6-1) 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 possi-

ble to execute a verify function without first program-

ming the EEPROM. A verify operation can only be

done once, immediately following the program

cycle.

FIGURE 6-1:

PROGRAMMING WAVEFORMS

FIGURE 6-2:

VERIFY WAVEFORMS

PWM

Enter Program

Mode

(Data)

(Clock)

Bit 1

Bit 2

Bit 3

Bit 14 Bit 15

Bit 16 Bit 17

Repeat 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

Acknowledge

S1

Bit 0

Bit 0

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

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

S1