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In addition, a number of constants are used to identify word length related values etc.;
These are listed in Table 1.5 .
A number of values are used by the ST20 to indicate the state of a process and other
conditions. These are listed in Table 1.6.
word offset
slot name
purpose
0
le.Index
contains the loop control variable
1
le.Count
contains number of iterations left to perform
Table 1.2 Loop end data structure
word offset
slot name
purpose
1
pp.Count
contains unsigned count of parallel processes
0
pp.IptrSucc
contains pointer to first instr uction of successor process
Table 1.3 Parallel process data structure
word offset
slot name
purpose
2
s.Back
back of waiting queue
1
s.Front
front of waiting queue
0
s.Count
number of extra processes that the semaphore will allow to continue
running on a
wait request
Table 1.4 Semaphore data structure
Name
Value
Meaning
BitsPerByte
8 The number of bits in a byte.
BitsPerWord
32 The number of bits in a word.
ByteSelectMask
#00000003
Used to select the byte select bits of an address.
WordSelectMask
#FFFFFFFC
Used to select the byte select bits of an address.
BytesPerWord
4 The number of bytes in a word.
MostNeg
#80000000
The most negative integer value.
MostPos
#7FFFFFFF The most positive signed integer value.
MostPosUnsigned
#FFFFFFFF
The most positive unsigned integer value.
PeripheralStart
#20000000
The lowest address reserved for memory-mapped on-
chip peripherals.
PeripheralEnd
#3FFFFFFF The highest address reserved for memory-mapped on-
chip peripherals.
Table 1.5 Constants used in the instruction descriptions