PSB21473FV13XT Infineon Technologies, PSB21473FV13XT Datasheet - Page 66

• Manufacturer Part Number: PSB21473FV13XT
• Manufacturer: Infineon Technologies

Specifications of PSB21473FV13XT

• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (min): 3.135V
• Operating Supply Voltage (max): 3.6V
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 144
• Lead Free Status / RoHS Status: Compliant

Data Sheet
The Stack Underflow Pointer STKUN
This non-bit addressable register is compared against the SP register after each
operation, which pops data from the system stack (eg. POP and RET instructions) and
after each addition to the SP register. If the content of the SP register is greater than the
the content of the STKUN register, a stack underflow hardware trap will occur.
Since the least significant bit of register STKUN is tied to '0' and bits 15 through 12 are
tied to '1' by hardware, the STKUN register can only contain values from F000
FFFE
STKUN (FE16
Bit
stkun
The Stack Underflow Trap (entered when (SP) > (STKUN)) may be used in two different
ways:
• Fatal error indication treats the stack underflow as a system error through the
associated trap service routine.
• Automatic system stack refilling allows to use the system stack as a 'Stack Cache'
for a bigger external user stack. In this case register STKUN should be initialized to a
value, which represents the desired highest Bottom of Stack address.
More details about the stack underflow trap service routine and virtual stack
management are given in chapter “System Programming”.
Scope of Stack Limit Control
The stack limit control realized by the register pair STKOV and STKUN detects cases
where the stack pointer SP is moved outside the defined stack area either by ADD or
SUB instructions or by PUSH or POP operations (explicit or implicit, ie. CALL or RET
instructions).
This control mechanism is not triggered, ie. no stack trap is generated, when
• the stack pointer SP is directly updated via MOV instructions
• the limits of the stack area (STKOV, STKUN) are changed, so that SP is outside of the
new limits.
15
r
1
H
14
r
.
1
13
r
1
H
/ 0B
Function
Modifiable portion of register STKUN
Specifies the upper limit of the internal system stack.
12
r
1
H
)
11
10
9
8
SFR
66
7
stkun
6
rw
5
4
Central Processor Unit
3
Reset Value: FC00
2
PSB 21473
1
2003-03-31
INCA-D
0
r
0
H
H
to