1. Description
In the specifications of the MCUs concerned, the bit 4 (CM04) of the
system clock control register 0 is set to 1 by default after the target
MCU has been reset, which enables the MCU's XCIN (P4_3) and XCOUT (P4_4)
pins to supply the XCIN clock to the system.
In some cases, however, CM04 is cleared to 0 after MCU reset, which
forces the XCIN (P4_3) and XCOUT (P4_4) pins to function as an I/O port.
If this is the case, no target systems synchronized with the XCIN clock
would be operated.
2. Conditions
This problem occurs if the following conditions are all satisfied:
(1) The R8C/Tiny E8a Emulator Debugger included in the product concerned
is running.
(2) The target system is designed with any member of the R8C/2G or R8C/2H
group of MCUs.
(3) Any of the following operations has been performed:
- Pressing of the CPU Reset button
- Selection of Reset CPU out of the Debug menu
- Hardware reset of the user board
3. Workaround
If your target system synchronized with the XCIN clock is debugged
using the E8a emulator, keep the CM04 bit set to 1 by describing it
in the user program.
4. Schedule of Fixing the Problem
We plan to fix this problem in the next release of the product.
