at83c5122 ATMEL Corporation, at83c5122 Datasheet - Page 22
at83c5122
Manufacturer Part Number
at83c5122
Description
At83c5123 C51 Microcontroller With Usb And Smart Card Reader Interfaces
Manufacturer
ATMEL Corporation
Datasheet
1.AT83C5122.pdf
(213 pages)
- Current page: 22 of 213
- Download datasheet (3Mb)
Dual Data Pointer
Register (DDPTR)
22
AT8xC5122/23
An access to external XRAM memory locations higher than the accessible size of the
memory (roll-over feature) will be performed with the MOVX DPTR instructions, with P0
and P2 as data/address busses, WR and RD as respectively write and read signals.
Accesses above XRAM size can only be done by the use of DPTR.
If EXTRAM=1 the MCU fetches the data from external XRAM Memory. There can be up
to 64 KBytes of external XRAM Memory.
The hardware configuration for external Data Memory Access is shown in Figure 10
Figure 10. Accessing to External XRAM Memory
MOVX @Ri and MOVX @DPTR will be similar to the standard 80C51. MOVX @ Ri will
provide an eight-bit address multiplexed with data on Port 0 and any output port pins
can be used to output higher order address bits. This is to provide the external paging
capability. MOVX @DPTR will generate a sixteen-bit address. Port 2 outputs the high-
order eight address bits (DPH) while Port0 multiplexes the low-order eight address bits
(DPL) with data. MOVX @ Ri and MOVX @DPTR will generate either read or write sig-
nals on WR and RD.
Ports P0, P2 are not affected and RD, WR signals are not activated during access to
internal XRAM.
Note that external XRAM Memory access is only available on High Pin Count Packages.
External Program Memory and external XRAM Memory may be combined if desired by
applying the RD and PSEN signals to the inputs of an AND gate and using the ouput of
the gate as the read strobe to the external program/data memory.
The additional data pointer can be used to speed up code execution and reduce code
size.
The dual DPTR structure is a way by which the chip will specify the address of an exter-
nal data memory location. There are two 16-bit DPTR registers that address the external
memory, and a single bit called DPS = AUXR1.0 (see Table 7) that allow the program
code to switch between them (Figure 11).
A T 8 x C 5 1 2 2 / 2 3
W R #
A L E
R D #
P 2
P 0
PSEN
RD
A D 7 : 0
A 1 5 : 8
L a t c h
STROBE
A 7 : 0
E X T E R N A L X R A M
A 1 5 : 8
A 7 : 0
D 7 : 0
O E
W R
M E M O R Y
4202E–SCR–06/06
Related parts for at83c5122
Image
Part Number
Description
Manufacturer
Datasheet
Request
R
Part Number:
Description:
INTERVAL AND WIPE/WASH WIPER CONTROL IC WITH DELAY
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
Low-Voltage Voice-Switched IC for Hands-Free Operation
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
MONOLITHIC INTEGRATED FEATUREPHONE CIRCUIT
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
AM-FM Receiver IC U4255BM-M
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
Monolithic Integrated Feature Phone Circuit
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
Multistandard Video-IF and Quasi Parallel Sound Processing
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
High-performance EE PLD
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
8-bit Flash Microcontroller
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
2-Wire Serial EEPROM
Manufacturer:
ATMEL Corporation
Datasheet:
Part Number:
Description:
U6046BREAR WINDOW HEATING TIMER / LONG-TERM TIMER
Manufacturer:
ATMEL Corporation
Datasheet: