AT83C5134 Atmel Corporation, AT83C5134 Datasheet - Page 30

• Manufacturer Part Number: AT83C5134
• Manufacturer: Atmel Corporation

Specifications of AT83C5134

• Max. Operating Frequency: 32 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Sram (kbytes): 1.25
• Eeprom (bytes): 512
• Operating Voltage (vcc): 2.7 to 3.6
• Timers: 4
• Mask Rom (kbytes): 8
• Watchdog: Yes

11. On-chip Expanded RAM (ERAM)
Figure 11-1. Internal and External Data Memory Address
30
AT83C5134/35/36
0FFh or 3FFh(*)
00
The AT83C5134/35/36 provides additional Bytes of random access memory (RAM) space for
increased data parameters handling and high level language usage.
AT83C5134/35/36 devices have an expanded RAM in the external data space; maximum size
and location are described in Table 11-1.
Table 11-1.
The AT83C5134/35/36 has on-chip data memory which is mapped into the following four sepa-
rate segments.
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.
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.
AT83C5134/35/36
1. The Lower 128 bytes of RAM (addresses 00h to 7Fh) are directly and indirectly
2. The Upper 128 bytes of RAM (addresses 80h to FFh) are indirectly addressable only.
3. The Special Function Registers, SFRs, (addresses 80h to FFh) are directly address-
4. The expanded RAM bytes are indirectly accessed by MOVX instructions, and with the
Part Number
ERAM
addressable.
able only.
EXTRAM bit cleared in the AUXR register (see Table 11-1)
Description of Expanded RAM
0FFh
80h
7Fh
00
indirect accesses
direct or indirect
ERAM Size
128 bytes
128 bytes
accesses
Internal
Internal
Upper
Lower
1024
RAM
RAM
0FFh
80h
direct accesses
Function
Register
Special
00FFh up to 03FFh (*)
Start
00h
(*) Depends on XRS1..0
0FFFFh
0000
Address
External
Memory
Data
3FFh
End
7683C–USB–11/07