AT89C5131A-RDTUM datasheet(50/188 Pages) ATMEL

50 / 188 page

4337K–USB–04/08

AT89C5130A/31A-M

12. On-chip Expanded RAM (ERAM)

The AT89C5130A/31A-M provides additional Bytes of random access memory (RAM) space for

increased data parameters handling and high level language usage.

AT89C5130A/31A-M devices have expanded RAM in external data space; maximum size and

location are described in Table 12-1.

The AT89C5130A/31A-M has on-chip data memory which is mapped into the following four sep-

arate segments.

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 address-

able only.

The expanded RAM bytes are indirectly accessed by MOVX instructions, and with the

EXTRAM bit cleared in the AUXR register (see Table 12-1)

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 sepa-

rate from SFR space.

Figure 12-1. Internal and External Data Memory Address

When an instruction accesses an internal location above address 7Fh, the CPU knows whether

the access is to the upper 128 bytes of data RAM or to SFR space by the addressing mode used

in the instruction.

Table 12-1.

Description of Expanded RAM

Part Number

ERAM Size

Address

Start

End

AT89C5130A/31A-M

1024

00h

3FFh

ERAM

Upper

128 bytes

Internal

RAM

Lower

128 bytes

Internal

RAM

Special

Function

80h

0FFh or 3FFh(*)

0FFh

External

Data

Memory

0000

00FFh up to 03FFh (*)

0FFFFh

indirect accesses

direct accesses

direct or indirect

accesses

7Fh

(*) Depends on XRS1..0

AT89C5131A-RDTUM Datasheet(PDF) 50 Page - ATMEL Corporation

AT89C5131A-RDTUM Datasheet(HTML) 50 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL