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(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.
15
14
13
CTBR
0
0
0
Bit Position
Bit Name
2
RXEN
1
TXPRE
TEN
The figure below shows the structure of the internal CAN test bus.
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
Note
4
) 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.
466
Chapter 14 FCAN Interface Function
Figure 14-19: CAN Test Bus Register (CTBR)
12
11
10
9
8
0
0
0
0
0
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.
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.
Enables internal test bus.
0: Internal test bus is disabled.
1: Internal test bus is enabled.
Figure 14-20: Internal CAN Test Bus Structure
TXPRE
CTXD1
CTXD2
CTXD3
RXEN
TEN
Preliminary User's Manual U15839EE1V0UM00
7
6
5
4
3
0
0
0
0
0
Function
Internal Test Bus
CRXDx
1
0
CAN module x
receive logic
Address
2
1
0
Note
Offset
RXEN TXPRE TEN
101CH
Initial
value
0000H
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