49
Subject to change without notice
S e r i a l b u s a n a l y s i s
important information, e.g. address and date of the message.
The number of rows in the table is identical to the number of
complete message frames in storage. The decoding results
may be saved as CSV file by using the soft menu key SAVE (e.g.
save to a USB stick).
Example of a I
2
C BUS table:
“Bus table: BUS1 (I2C: Clock SCL = D0, Dates SDA = D1)“
Frame,Mark,Start time[s],Type,ID,Length,Date,Condition
1,,-197.89200e-6,Read,0x2D,5,0xF110E55D31,OK
2,,28.00000e-9,Write,0x42,8,0xEB8DC599AE5D6FC0,OK
3,,217.74000e-6,Write,0x3B,6,0xA113B7263E5B,OK
4,,376.07200e-6,Read,0x0E,6,0x55C3EB71D9E8,OK
5,,613.58000e-6,Write,0x66,8,0x91B86EE6655E2300,Data Error0
A BUS table can only be stored if the STOP mode is
active.
The soft menu key
TRACK FRAME
allows you to scroll through
the BUS table and simultaneously jump to the corresponding
position in the memory via universal knob to display details
on the screen. However, this is only possible if acquisition has
been stopped. This option is also available in the short menu
BUS via soft menu key Trk (= Track). If you activate the soft
menu key FRAME TIME DIFFERENCE (highlighted in blue),
the time difference to the previous frame (data packet) will
be displayed in the BUS table. This column will be labeled in
the table as “Time diff. “. If this function is deactivated, the
absolute time in relation to the trigger point will be displayed
in the column “Start time”. The soft menu key Tab in the BUS
short menu allows you to activate or deactivate the BUS table
without opening a menu.
You can use the soft menu item POSITION to move the table
to the top or bottom of the screen. In addition, it is possible
to display the BUS table in full screen. Select the position via
universal knob in the BUS menu or directly via soft menu key
Pos in the BUS short menu.
13.2 Parallel BUS
The HMO series is able to analyze up to 7 bit lines. The soft menu
key
BUS WIDTH
and the universal knob allow you to select the
number of bit lines. You can use the
soft menu keys
PREV. BIT
and
NEXT BIT
(or the universal knob) to move the position of the
SOURCE
selection bar for individual BUS bits. The selected bit
is highlighted in blue. To trigger on parallel buses, it is recom-
mended to use the logic trigger (see chapter 6.5).
13.3 I
2
C BUS
The I
2
C bus is a two-wire bus which was developed by Philips
(today known as NXP Semiconductor). The HMO series supports
the following bit rates (for measurements without measuring
object via BUS SIGNAL SOURCE):
– 100 kBit/s (Standard Mode)
– 400 kBit/s (Fast Mode)
– 1000 kBit/s (Fast Mode Plus).
Use the soft menu PROBE COMP & BUS SIGNAL SOURCE
to select the respective clock rate in the SETUP menu (page
2|2).
Fig. 13.4: I
2
C BUS signal source
A I
2
C BUS has the following properties:
– Two wire bus (2-wire): Clock (SCL) and data (SDA)
– Master-Slave Communication: the master provides the clock
pulse and selects the slave
– Addressing: Each slave can be addressed via unique ad
-
dress; multiple slaves can be linked with each other and
can be addressed by the same master
– Read/Write bit: Master reads data (=1) or writes data (=0)
– Acknowledge: issued after each byte
The format of a simple I
2
C message (frame) with an address
length of 7 bit is structured as follows:
– Start condition: Falling slope on SDA (Serial Data), while
SCL (Serial Clock) is HIGH
– 7 bit address (write or read slave)
– Read/Write bit (R/W): Indicates, if the data is to be written
or read out from the slave
– Acknowledge bit (ACK): Is issued by the recipient of the
previous byte if transmission was successful (exception: for
read access, the master terminates the data transmission
with a NACK bit after the last byte)
– Data: a series of data bytes with a ACK bit after each byte
– Stop condition: rising slope on SDA (Serial Data), while SCL
(Serial Clock) is HIGH
Fig. 13.5: I
2
C 7 bit address
Fig. 13.3: Example I
2
C BUS with BUS table
