MCRF450 datasheet(38/50 Pages) MICROCHIP

38 / 50 page

MCRF450/451/452/455

DS40232H-page 38

 2003 Microchip Technology Inc.

EXAMPLE 9-3:

TO WRITE DATA INTO THE DEVICE

The Interrogator command structure for writing (see Section 6.2.1 “Structure of Read/ Write Command Signals”) is:

Calibration pulse + Writing Command (MSN first) + Address (MSN first) + Data (LSN first) + Parity/CRC (LSN first)

If the Interrogator wants to write data “0123cdef (hex, MSB to LSB)” to Block 5, the following message will be sent:

Calibration pulse + Write Command (MSN first) + Address (MSN first) + Data (LSN first) + Parity/CRC (LSN first)

= Cal. pulse + 101 (Write command) + 00101 (address) + f e d c 3 2 1 0 (data, hex) + CRC

= Calibration pulse + a 5 f e d c 3 2 1 0 6 0 2 e (hex string)

The hex string above is encoded with the 1-of-16 PPM signals. See Figure 6-10 for the 1-of-16 PPM representation of

hex values.

Referring to Figure 6-10, the gap positions in the 1-of-16 PPM for the above hex string are:

Positions 10 (a), 5 (5), 15 (f), 14 (e), 13 (d), 12 (c), 3 (3), 2 (2), 1 (1), 0 (0), 6 (6), 0 (0), 2 (2), e (14).

Device Response:

If writing is completed: The device sends the written data after 5 msec of EEPROM writing time.

If writing is failed due to insufficient programming voltage for unprotected block: The device sends the current

block data after about 500

µsec of delay.

If writing is failed because the block is write-protected block: The device sends the current block data immediately

after the command.

If writing is failed due to incorrect CRC: The device does not respond at all.

FIGURE 9-1:

FLOW CHART FOR THE DEVICE RESPONSE TO THE WRITE COMMAND

Note:

CRC = CRC for the Write command, address, and data. Calibration pulse is not included for the CRC

calculation. See Application Note AN752 (DS00752) for the CRC calculation algorithm.

Wait for

Command

Received

Write Command?

Is CRC

Correct?

Read and Send

Block Data

EEPROM

Start High Voltage

and Wait for about

500

µsec

Have sufficient

Write EEPROM

Data (5 msec)

Yes

Is the Block

Write-Protected?

programming?

High Voltage for

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