W78ERD2_07 Datasheet, PDF (59/76 Pages) Winbond – 8-BIT MICROCONTROLLER

W78ERD2/W78ERD2A
MOVC Inhibit
This bit is used to restrict the accessible region of the MOVC instruction. It can prevent a MOVC
instruction in external program memory from reading the internal program code. When this bit is set to
logic-0, a MOVC instruction in external program memory space can only access code in external
memory, not in internal memory. A MOVC instruction in internal program memory can always access
both internal and external memory. If this bit is logic-1, there are no restrictions on MOVC.
Encryption
This bit is used to enable and disable the encryption logic for code protection. Once encryption is
enabled, the data presented on port 0 is encoded via encryption logic. This bit can be reset only by
erasing the whole chip.
Oscillator Control
The gain of the on-chip oscillator amplifier can be reduced by bit B7 in the option bits register. If bit 7
is set to zero, the gain is cut in half.
According the circuit in Figure 20-1, the values of R, C1 and C2 may need some adjustment when
running at lower gain. Furthermore, reducing the gain by one-half may improperly affect an external
crystal running at frequencies above 25 MHz.
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Publication Release Date: February 14, 2007
Revision A10