KROHNE UFC 500 HART User Manual

Page 36

HARTô Smart Communications Protocol

UFC500 Command Specification Rev: 2.0 Release Date: 9 Jun 2001

Page

8.18

Command #150

Enable/Disable Password Protection

Installs/uninstalls write protection. Two transaction are implemented: Transaction #1 disables write protection, in this
case a correct password must be ìshownî to transmitter. If protection is disabled and device is open for write operations,
any of two transactions can be used to enable manually-set password. Then the contents of Password field for
Transaction #1 is ignored. It is not possible to change the password itself via bus!

TRANSACTION #0

REQUEST DATA BYTES

#0
WRITE
PROT
CONTROL

RESPONSE DATA BYTES

#0
WRITE
PROT
CONTROL

TRANSACTION #1

REQUEST DATA BYTES

...

WRITE

PROT

CODE

CONTROL

BYTE #0

BYTE #4

RESPONSE DATA BYTES

#0
WRITE
PROT
CONTROL

Data Byte #0

Write protect control, being a negation of the Write Protect Code (available via Command
#15, Read Primary Variable Output Information):

0 - Password is enabled,
1 - Password is disabled.

Data Byte #1-#5

The instrument password. The encoding scheme is as follows: the ìRightî-key of device
keypad is coded by 0x8, ìEnterî-key - by 0x4 and ìUpî-key - by 0x1. Then the nine
keystokes of the password are packed into 5 bytes in a straightforward way: the first
password symbol is placed in the four most significant bits of Data Byte #1, the second
password symbol - in the four least significant bits of Data Byte #1, etc. The last Data Byte
#5 is zero terminated.
For example, some arbitrary key combination ìRight-Right-Up-Up-Up-Right-Enter-Up-Upî
will result in a byte sequence 0x88, 0x11, 0x18, 0x41, 0x10.

NOTE: Any nonzero value of WriteProtectControl will be interpreted by transmitter as a request to disable protection
and responded back as м1о.