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Chapter 31 External Bus
12.Procedure for Setting a Register
12. Procedure for Setting a Register
This section explains the procedure for setting a register.
■ Procedure for Setting a Register
Using the following procedures to make external bus interface settings:
1. Before rewriting the contents of a register, be sure to set the CSER register so that the corresponding area is
not used (0). If you change the settings while 1 is set, access before and after the change cannot be
guaranteed.
2. Use the following procedure to change a register:
• Set 0 for the CSER bit corresponding to the applicable area.
• Set both ASR and ACR at the same time using word access.
• Set AWR.
• Set the CHER bit corresponding to the applicable area.
• Set the CSER bit corresponding to the applicable area.
3. The CS0 area is enabled after a reset is released. If the area is used as a program area, the register contents
need to be rewritten while the CSER bit is 1. In this case, make the settings described in 2) to 4) above in the
initial state with a low-speed internal clock. Then, switch the clock to a high-speed clock.
4. Use the following procedure to change the register value in an area for which prefetch:
• Set 0 for the bit of CSER corresponding to the applicable area.
• Set 1 for both the PSUS bit and PCLR bit of the TCR register.
• Set both ASR and ACR at the same time using word access.
• Set AWR.
• Set the CHER bit corresponding to the applicable area.
• Set 0 for both the PSUS bit and PCLR bit of the TCR register.
• Set 1 for the bit of CSER corresponding to the applicable area.