© 2011 Microchip Technology Inc.

DS41098D-page 13

HCS201

6.0

PROGRAMMING THE HCS201

When using the HCS201 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 cycle 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 DATA line high, after the S2 line

has been held high for the appropriate length of time

line (Table 6-1 and Figure 6-1). After the Program

mode is entered, a delay must be provided to the

device for the automatic bulk write cycle to complete.

This will write all locations in the EEPROM to an all

zeros pattern. The device can then be programmed by

clocking in 16 bits at a time, using S2 as the clock line

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

loaded, a programming delay is required for the internal

program cycle to complete. This delay can take up to

Twc. After every 16-bit word is written to the HCS201,

the HCS201 will signal that the write is complete by

low (if the oscillator was perfectly tuned) on DATA.

These will continue until S2 is dropped. The first pulse’s

width should NOT be used for calibration. 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 S2 line and reading the data bits

on DATA. For security reasons, it is not possible to exe-

cute a verify function without first programming 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

Note:

To ensure that the device does not acci-

dentally enter Programming mode, DATA

should never be pulled high by the circuit

connected to it. Special care should be

taken when driving PNP RF transistors.

DATA

Enter Program

Mode

(Data)

(Clock)

Note 1: S0 and S1 button inputs to be held to ground during the entire programming sequence.

Bit 0

Bit 1

Bit 2

Bit 3

Bit 14

Bit 15

Bit 16

Bit 17

Repeat for each word (12 times)

S2

Data for Word 1

Initiate Data

Polling Here

Write Cycle

Complete Here

Calibration Pulses

Ack

Ack

Ack

DATA

(Clock)

(Data)

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

End of Programming Cycle

Beginning of Verify Cycle

Bit 1 Bit 2

Bit 3

Bit 15

Bit 14

Bit 16 Bit 17

Bit190 Bit191

Data from Word 0

S2

Bit 0

Bit191

Bit190

Ack