Siemens EF 88H Series Bedienungsanleitung PDF herunterladen (Seite 10)

Semiconductor Group 3 - 2

Memory Organization

3.1 Program Memory, ROM Protection

The

SAB 83C517A-5 has 32 Kbyte of on-chip ROM, while the SAB 80C517A has no internal

ROM. The program memory can externally be expanded up to 64 Kbyte. Pin EA

controls whether

program fetches below address 8000H are done from internal or external memory.

As a new feature the SAB 83C517A-5 offers the possibillity of protecting the internal ROM against

unauthorized access. This protection is implemented in the ROM-Mask. Therefore, the decision

ROM-Protection ’yes’ or ’no’ has to be made when delivering the ROM-Code. Once enabled, there

is no way of disabling the ROM-Protection.

Effect : The access to internal ROM done by an externally fetched MOVC instruction is disabled.

Nevertheless, an access from internal ROM to external ROM is possible.

To verify the read protected ROM-Code a special ROM-Verify-Mode is implemented. This mode

also can be used to verify unprotected internal ROM.

ROM-Protection ROM-Verification Mode

(see ’AC Characteristics’)

Restrictions

no ROM-Verification Mode 1

(standard 8051 Verification Mode)

ROM-Verification Mode 2

–

yes ROM-Verification Mode 2 – standard 8051 Verification

Mode is disabled

– externally applied MOVC

accessing to internal ROM

is disabled

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 136 137

Keine Kommentare

Siemens EF 88H Series Bedienungsanleitung Seite 10