NEC MuPD70F3187, User Manual

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Chapter 18 AFCAN Controller
User’s Manual U16580EE3V1UD00
18.6 Bit Set/Clear Function
The CAN control registers include registers whose bits can be set or cleared via the CPU and via the
CAN interface. An operation error occurs if the following registers are written directly. Do not write any
values directly via bit manipulation, read/modify/write, or direct writing of target values.
• CANn global control register (CnGMCTRL)
• CANn global automatic block transmission control register (CnGMABT)
• CANn module control register (CnCTRL)
• CANn module interrupt enable register (CnIE)
• CANn module interrupt status register (CnINTS)
• CANn module receive history list register (CnRGPT)
• CANn module transmit history list register (CnTGPT)
• CANn module time stamp register (CnTS)
• CANn message control register (CnMCTRLm)
All the 16 bits in the above registers can be read via the usual method. Use the procedure described in
Figure 18-23 below to set or clear the lower 8 bits in these registers.
Setting or clearing of lower 8 bits in the above registers is performed in combination with the higher 8
bits (refer to the bit status after set/clear operation is specified in <~Reference>Figure 18-26). Figure
18-23 shows how the values of set bits or clear bits relate to set/clear/no change operations in the cor-
responding register.
Figure 18-23: Example of bit setting/clearing operations
0 0 0 0 0 0 0 0 1 1 0 1 0 0 0 1
0 0 0 0 1 0 1 1 1 1 0 1 1 0 0 0
set 0 0 0 0 1 0 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1
clear 1 1 0 1 1 0 0 0
Set
No change
Clear
Bit status
Register’s current value
Write value
Register’s value after
write operation
Clear
Clear No change
No change Set