DATA SHEET
HAL855
5. Programming of the Sensor
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 HAL855.
This stopping command can be a further program-
ming command or a read command (see Fig. 5–5
on page 36).
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.
– 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.
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
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.
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:
– 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.
– 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.
t
t
f
r
high-level
logical 0
t
t
p0
p0
or
low-level
– 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.
t
p1
high-level
t
t
p0
– Programming the EEPROM cells
p0
logical 1
low-level
or
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
HAL855 answers with an acknowledge pulse on its
t
p1
Fig. 5–1: Definition of logical 0 and 1 bit
Micronas
Nov. 26, 2008; DSH000149_003EN
33
MICRONAS [ MICRONAS ]
