5 Allocation of Buffer Memories
5.1 Buffer Memories (BFM) Lists
32
FX
3U
-J1939 User's Manual
5. Allocation of Buffer Memories
5.1
Buffer Memories (BFM) Lists
Caution
• Do not access buffer memory (BFM) that is marked as "not used" (Ex. BFM #0 to #19, #23, #31 to #34, #49
to #99, #400, #480 to #499, etc.) by FROM/TO instructions, etc. Accessing these buffer memories may
cause abnormal behavior of the FX
3U
-J1939.
• When BFM #21, #24, #25 bit 2, #26 or #27 is written to, FX
3U
-J1939 stores the state of the corresponding
BFM in the built-in flash ROM. The maximum number of writes to the built-in flash ROM is 10,000 times.
Therefore, when creating a program, do not frequently write to such buffer memories.
Note
• When writing to a BFM that contains any bits marked as "reserved" (Ex. BFM #20 bit 1 to bit 15, BFM #22
bit 3 to bit 15, etc), set such bits to OFF.
Setting these flags to ON may cause abnormal behavior of the FX
3U
-J1939.
• The state of BFM #40 to #48, #100 to #399, #500 to #973, #1100 to #1267, #1900 to #1927, #3000 to
#3879 is stored in the built-in flash ROM by turning ON BFM #22 bit 0. The buffer memories that are stored
depend on the function mode (BFM #21).
For further information, refer to the following section.
Therefore, when creating a program, do not frequently switch BFM #22 bit 0 from OFF to ON.
Refer to Section 5.5
BFM No.
Description
Default
value
Read/
Write
Stored to
Flash
ROM
Reference
BFM #0 to #19
Not used
-
-
-
-
BFM #20
Data exchange control
K0
R/W
-
Section 5.3
BFM #21
Function mode
K1939
R/W
Section 5.4
BFM #22
Save/Restore configuration
K0
R/W
-
Section 5.5
BFM #23
Not used
-
-
-
-
BFM #24
Baud rate
K250
R/W
Section 5.6
BFM #25
Communication status
K4
R/W
*1
Section 5.7
BFM #26
FROM/TO Watchdog (
10 ms)
K20
R/W
Section 5.8
BFM #27
Node address (address claim start address)
K128
R/W
Section 5.9
BFM #28
Node address (current address)
K254
R
-
Section 5.10
BFM #29
Error status
K0
R/W
-
Section 12.2
BFM #30
Module ID code
K7180
R
-
Section 5.12
BFM #31 to #34
Not used
-
-
-
-
BFM #35
CAN transmission error counter
K0
R
-
Section 5.13
BFM #36
CAN reception error counter
K0
R
-
Section 5.14
BFM #37
Baud rate display (
0.1 kbps)
K2500
R
-
Section 5.15
BFM #39
BFM setting error display
K0
R
-
Section 5.16
BFM #40 to #48
64 bit ECU NAME according to J1939-81
-
R/W
*2
Section 5.17
BFM #49 to #99
Not used
-
-
-
-
BFM #100 to #399
Data (read/write)
K0
R/W
*2
*3
BFM #400
Not used
-
-
-
-
BFM #401 to #479
Message error code list
K0
R/W
-
Section 5.19
BFM #480 to #499
Not used
-
-
-
-
BFM #500 to #973
J1939 message configuration area
-
R/W
*2
Section 6.2
