SAF-C161U-LF V1.3 Infineon Technologies, SAF-C161U-LF V1.3 Datasheet - Page 406

• Manufacturer Part Number: SAF-C161U-LF V1.3
• Description: IC MCU ISDN 16BIT TTL TQFP-100
• Manufacturer: Infineon Technologies
• Series: C16xxr

Specifications of SAF-C161U-LF V1.3

• Core Processor: C166
• Core Size: 16-Bit
• Speed: 36MHz
• Connectivity: EBI/EMI, SPI, UART/USART, USB
• Peripherals: POR, PWM, WDT
• Number Of I /o: 56
• Program Memory Type: ROMless
• Ram Size: 3K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 100-LFQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -
• Data Converters: -
• Other names: SAFC161ULFV1.3X; SAFC161ULFV13XP; SP000007502

Data Sheet
Alternate Bank of Registers: Upon entry into a subroutine, it is possible to specify a
new set of local registers by executing the SCXT (switch context) instruction. This
mechanism does not provide a method to recursively call a subroutine.
Saving and Restoring of Registers: To provide local registers, the contents of the
registers which are required for use by the subroutine can be pushed onto the stack and
the previous values be popped before returning to the calling routine. This is the most
common technique used today and it does provide a mechanism to support recursive
procedures. This method, however, requires two machine cycles per register stored on
the system stack (one cycle to PUSH the register, and one to POP the register).
Use of the System Stack for Local Registers: It is possible to use the SP and CP to
set up local subroutine register frames. This enables subroutines to dynamically allocate
local variables as needed within two machine cycles. A local frame is allocated by simply
subtracting the number of required local registers from the SP, and then moving the
value of the new SP to the CP.
This operation is supported through the SCXT (switch context) instruction with the
addressing mode 'reg, mem'. Using this instruction saves the old contents of the CP on
the system stack and moves the value of the SP into CP (see example below). Each local
register is then accessed as if it was a normal register. Upon exit from the subroutine,
first the old CP must be restored by popping it from the stack and then the number of
used local registers must be added to the SP to restore the allocated local space back
to the system stack.
Note: The system stack is growing downwards, while the register bank is growing
Figure 123
upwards.
Local Registers
Old SP
New CP
New SP
Old CP Contents
R4
R3
R2
R1
R0
406
Old Stack
Allocated
Register
Newly
Stack
Bank
Area
Area
New
System Programming
2001-04-19
C161U