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Chapter 14
FCAN Interface Function
Preliminary User’s Manual U15839EE1V0UM00
(9)
CAN test bus register (CTBR)
For test purposes an internal test bus is available. The CTBR register controls this test bus capa-
bility.
This register can be read and written in 8-bit and 16-bit units.
Figure 14-19:
CAN Test Bus Register (CTBR)
The figure below shows the structure of the internal CAN test bus.
Figure 14-20:
Internal CAN Test Bus Structure
Remarks: 1. Both, TEN bit and RXEN bit must be set (1) to use the internal CAN bus.
2. Using the internal CAN bus connects all CAN modules (CAN module 1 to CAN module
4
Note
) to one internal CAN bus. The internal CAN bus is used to operate the FCAN sys-
tem without any external hardware (e.g. CAN transceiver, bus harness, etc.).
3. x = 1 to 4
Note: CAN module 3 and CAN module 4 are available in the derivatives µPD703129 (A) and
µPD703129 (A1) only.
Caution:
The internal test bus must only be used when none of the CAN modules are con-
nected to a CAN bus.
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Address
Offset
Note
Initial
value
CTBR
0
0
0
0
0
0
0
0
0
0
0
0
0
RXEN TXPRE TEN
101CH
0000H
Bit Position
Bit Name
Function
2
RXEN
Enables the receive line.
0: CAN module receive lines are input from the corresponding CANxRX pins.
1: CAN module receive lines are input from to the internal test bus.
1
TXPRE
Presets the transmit lines.
0: No preset on the transmit lines.
1: Error injection into the internal test bus by forcing all transmit pins to a
dominant level.
TEN
Enables internal test bus.
0: Internal test bus is disabled.
1: Internal test bus is enabled.
TXPRE
CTXD1
CTXD2
CTXD3
Internal Test Bus
RXEN
TEN
0
1
CAN module x
receive logic
CRXDx
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