Rainbow Electronics T89C5121 - Manual (Page 61)

61
A/T8xC5121
4164G–SCR–07/06
Memory Mapping In the products versions, the following internal spaces are defined:
• RAM
• XRAM
• CRAM: 16 KBytes Program RAM Memory
• ROM
The specific accesses from/to these memories are:
• XRAM: if the bit RPS in RCON (described below) is reset, MOVX instructions
address the XRAM space.
• CRAM: if the bit RPS in RCON is set, MOVX instructions address the CRAM
space.
Table 46. RCON Register
Reset Value = XXXX 0XXXb
T89C5121 Flash ROM Version Three memory blocks are implemented
• An internal serial EEPROM can be loaded from external with the application
program.
• The ROM memory contains the Bootloader program. The entry point is located at
address F800h. The lower 14K Bytes between address C000h and F7FFh is, also,
used for the Bootloader program.
• The CRAM is the application program memory. This memory is mapped in the
External RAM space. The bit RPS in RCON (SFR address 0D1h) is set to map the
CRAM space during MOVX instructions
For first programming or an update, the program can be downloaded in the internal
EEPROM (and in the CRAM) from an external device:
• Either an external EEPROM if detected
• or from a host through RS232 serial communication.
For this purpose, an In-System Programming (ISP) is supplied in a Bootloader. This
Bootloader is program masked in ROM space.
The Hardware Byte BLJRB value is 0.
As described on page 7, after Reset, the Bootloader program is executed.
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 set this bit.
3 RPS
CRAM space map bit
Set to map the CRAM space during MOVX instructions
Clear to map the Data space during MOVX. This bit has priority over the EXTRAM
bit.
2-0 -
Reserved
The value read from this bit is indeterminate. Do not set this bit.