ST10R272L - CENTRAL PROCESSING UNIT
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the limits of the stack area (STKOV, STKUN) are changed, so that SP is outside of the
new limits.
STKUN (FE16h / 0Bh)
SFR
Reset Value: FC00h
The multiply/divide high register MDH
This register is a part of the 32-bit multiply/divide register - used by the CPU for multiplication
or division. After a multiplication, this non bit-addressable register represents the high order
16 bits of the 32-bit result. For long divisions, the MDH register must be loaded with the high
order 16 bits of the 32-bit dividend, before the division is started. After any division, the
MDHregister contains the 16-bit remainder.
Whenever this register is updated via software, the Multiply/Divide Register In Use (MDRIU)
flag in the Multiply/Divide Control register (MDC) is set to ’1’.
When a multiplication or division is interrupted before its completion, and when a new
multiply or divide operation is to be performed within the interrupt service routine, registers
MDH, MDL and MDC must be saved, to avoid erroneous results.
A detailed description of how to use the MDH register for programming multiply and divide
algorithms can be found in “SYSTEM PROGRAMMING” on page 303.
The multiply/divide low register MDL
This register is a part of the 32-bit multiply/divide register used by the CPU for multiplication
or division. After a multiplication, this non-bit addressable register represents the low order
16 bits of the 32-bit result. For long divisions, the MDL register must be loaded with the low
order 16 bits of the 32-bit dividend before the division is started. After any division, register
MDL represents the 16-bit quotient.
Whenever this register is updated via software, the Multiply/Divide Register In Use (MDRIU)
flag in the Multiply/Divide Control register (MDC) is set to '1'. The MDRIU flag is cleared,
whenever the MDL register is read.
Bit
Function
stkun
Modifiable portion of register STKUN
Specifies the upper limit of the internal system stack.
1
0
1
5
4
3
2
1
0
11
10
9
8
7
6
15
14
13
12
r
rw
r
r
r
1
1
r
stkun
