Rainbow Electronics AT89C5122 - Manual (Page 26)

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AT8xC5122/23
4202E–SCR–06/06
Reset Value = XXXX 0XXXb
AT8xC5122’s CRAM and E2PROM Versions
The AT8xC5122’s CRAM and E2PROM versions implements :
- 32 KB of ROM mapped from 8000 to FFFF in which is embedded a bootloader for In-
System Programming feature
- 32 KB of CRAM (Code RAM) , a volatile program memory mapped from 0000 to 7FFF
In CRAM versions only :
- 512 bytes of E2PROM can be optionally implemented to store permanent data
In E2PROM version :
- 32KB of E2PROM are implemented to store permanent code
Warnings :
– some bytes of user program memory space are reserved for bootloader
configuration. Depending on the configuration, up to 256 bytes of code may
be not available for the user code from 7F00h location. Refer to bootloader
datasheet for further details.
– Port P3.7 may be used by the bootloader as a hardware condition at reset to
select the In-System Programming mode. Once the bootloader has started,
the P3.7 Port is no more used.
Table 8. CRAM Configuration Register - RCON (D1h)
7 6 5 4 3 2 1 0
- - - - RPS - - -
Bit
Number
Bit
Mnemonic Description
7 - 4 -
Reserved
The value read from this bit is indeterminate. Do not change these bits.
3 RPS
CRAM Memory Mapping Bit
Set to map the CRAM memory during MOVX instructions
Clear to map the XRAM memory during MOVX.
This bit has priority over the EXTRAM bit.
2-0 -
Reserved
The value read from this bit is indeterminate. Do not change these bits.