HAL855UT-K datasheet(33/42 Pages) MICRONAS

33 / 42 page

DATA SHEET

HAL855

Micronas

Nov. 26, 2008; DSH000149_003EN

5. Programming of the Sensor

5.1. Definition of Programming Telegram

The sensor is addressed by modulating a serial tele-

gram on the supply voltage. The sensor answers with

a serial telegram on the output pin.

The bits in the serial telegram have a different bit time

for the VDD-line and the sensors answer. The bit time

for the VDD-line is defined through the length of the

Sync Bit at the beginning of each telegram. The bit

time for the sensors answer is defined through the

Acknowledge Bit.

A logical “0” is coded as no output level change within

the bit time. A logical “1” is coded as an output level

change between 50% and 80% of the bit time. After

each bit, an output level change occurs.

5.2. Definition of the Telegram

Each telegram starts with the Sync Bit (logical 0), 3

bits for the Command (COM), the Command Parity Bit

(CP), 4 bits for the Address (ADR), and the Address

Parity Bit (AP).

There are 4 kinds of telegrams:

– Write a register (see Fig. 5–2 on page 35)

After the AP Bit, follow 14 Data Bits (DAT) and the

Data Parity Bit (DP). If the telegram is valid and the

command has been processed, the sensor answers

with an Acknowledge Bit (logical 0) on the output.

Note: The sensor can only be programmed with pro-

grammer board version 5.1. If you have an older

version, please contact Micronas or your sup-

plier.

– Read a register (see Fig. 5–3 on page 35)

After evaluating this command, the sensor answers

with the Acknowledge Bit, 14 Data Bits, and the

Data Parity Bit on the output.

– Programming the EEPROM cells

In order to permanently store the written data into

the EEPROM cells, an erase and program com-

mand have to be sent to the sensor. After the recog-

nition of the erase and program commands, the

HAL 855 answers with an acknowledge pulse on its

output signal. After the acknowledge pulse, a pulse

on the VDD-line is created to start the charging of

the EEPROM cells. Then, the supply voltage is kept

constant during the charging time. To stop the

charging, a further command is sent to the HAL 855.

This stopping command can be a further program-

ming command or a read command (see Fig. 5–5

on page 36).

– Lock a sensor

To lock the EEPROM registers, the lock bit has to be

programmed. Write the lock bit into the lock register.

If the telegram is valid and the command has been

processed, the sensor answers with an Acknowl-

edge Bit (logical 0) on the output. In order to store

the lock bit permanently, an erase and program

command have to be sent to the sensor. The same

procedure as mentioned above (Programming the

EEPROM cells Fig. 5–5 on page 36). The EEPROM

registers are locked after a power on reset.

Note: It is mandatory to lock the sensor before per-

forming any kind of reliability tests or after the

last programming of the sensor. The HAL855

has its full performance only after setting the

LOCK bit.

– Activate a sensor (see Fig. 5–4 on page 35)

If more than one sensor is connected to the supply

line, selection can be done by first deactivating all

sensors. With an Activate pulse on the appropriate

output pin, an individual sensor can be selected. All

following commands will only be accepted from the

activated sensor.

Fig. 5–1: Definition of logical 0 and 1 bit

tp0

logical 0

high-level

low-level

tp0

logical 1

high-level

low-level

tp0

tp1

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