SAB80C517A-N18 Siemens Semiconductor Group, SAB80C517A-N18 Datasheet - Page 19

• Manufacturer Part Number: SAB80C517A-N18
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: Siemens Semiconductor Group

Program Memory ('Code Space')
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 possibility 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:
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
no
yes
Semiconductor Group
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.
ROM-Verification Mode
(see 'AC Characteristics')
ROM-Verification Mode 1
(standard 8051 Verification Mode)
ROM-Verification Mode 2
ROM-Verification Mode 2
18
Restrictions
–
– externally applied MOVC
– standard 8051
SAB 80C517A/83C517A-5
Verification Mode is
disabled
accessing internal ROM
is disabled
1994-05-01