AT83EC5123 ATMEL Corporation, AT83EC5123 Datasheet - Page 148

• Manufacturer Part Number: AT83EC5123
• Description: (AT8xx512x) Smart Card Reader ICs
• Manufacturer: ATMEL Corporation

Data Memory
Management
Expanded RAM (XRAM)
148
AT8xC5122/23
The AT8xC5122/23 and AT8xC5123 provides additional Bytes of random access mem-
ory (RAM) space for increased data parameter handling and high level language usage.
AT8xC5122/23 and AT8xC5123 devices have expanded RAM in external data space;
maximum size and location are described in Table 110.
The AT8xC5122/23 and AT8xC5123 have internal data memory that is mapped into four
separate segments.
The four segments are:
•
•
•
•
The lower 128 bytes can be accessed by either direct or indirect addressing. The Upper
128 bytes can be accessed by indirect addressing only. The Upper 128 bytes occupy
the same address space as the SFR. That means they have the same address, but are
physically separate from SFR space.
Table 110. Description of Expanded RAM
AT8xC5122 and
AT8xC5123
The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly
addressable.
The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable
only.
The Special Function Registers, SFRs, (addresses 80h to FFh) are directly
addressable only.
The expanded RAM bytes are indirectly accessed by MOVX instructions, and with
the EXTRAM bit cleared in the AUXR register (see Table 108 on page 146)
XRAM size
512
Start
00h
Address
4202B–SCR–07/03
1FFh
End