AT89LP51RB2 Atmel Corporation, AT89LP51RB2 Datasheet - Page 23

• Manufacturer Part Number: AT89LP51RB2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RB2

• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 42
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Adc Channels: 7
• Adc Resolution (bits): 10
• Adc Speed (ksps): 153.8
• Sram (kbytes): 1.375
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

3.5
3722A–MICRO–10/11
Extended Stack
The AT89LP51RB2/RC2/IC2 provides an extended stack space for applications requiring addi-
tional stack memory. By default the stack is located in the 256-byte IDATA space of internal data
memory. The IDATA stack is referenced solely by the 8-bit Stack Pointer (SP: 81H). Setting the
XSTK bit in AUXR1 (see
the EDATA space for up to 2KB of stack memory. The extended stack is referenced by an 11-bit
pointer formed from SP and the three LSBs of the Extended Stack Pointer (SPX: EFH) as shown
in
overflow to the EDATA stack or vice versa. The stack and extended stack are mutually exclusive
and SPX is ignored when XTSK = 0. An application choosing to switch between stacks by tog-
gling XSTK must maintain separate copies of SP for use with each stack space. Interrupts
should be disabled while swapping copies of SP in such an application to prevent illegal stack
accesses.
All interrupt calls and PUSH, POP, ACALL, LCALL, RET and RETI instructions will incur a one
or two-cycle penalty while the extended stack is enabled, depending on the number of stack
access in each instruction. The extended stack may only exist within the internal EDATA space;
it cannot be placed in XDATA. The stack will continue to use EDATA even if EDATA is disabled
by setting EXRRAM = 1.
Figure 3-16. Stack Configurations
Figure
3-16. SP is shared between both stacks. Note that the standard IDATA stack will not
7
SP
Table
0
AT89LP51RB2/RC2/IC2 Preliminary
FFh
00h
5-6) enables the extended stack. The extended stack resides in
XSTK = 0
IDATA
(256)
2
SPX
0
7
SP
0
7FFh
00h
XSTK = 1
EDATA
(2K)
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