NS32FV16 Datasheet, PDF (11/104 Pages) Texas Instruments – Advanced Imaging/Communication Signal Processors

2 0 Architectural Description (Continued)
The X Y and Z registers are used for addressing up to
The OVF register holds the current status of the DSPM
three vector operands They are 32-bit registers with three
arithmetic unit It has two fields OVF and SAT The OVF bit
fields ADDRESS INCREMENT and WRAP-AROUND The
is set to ‘‘1’’ whenever an overflow is detected in the DSPM
value in the ADDRESS field specifies the address of a word
34-bit ALU (e g bits 32 and 33 of the ALU are not equal)
in the on-chip memory This field has 16 bits and can ad-
No overflow detection is provided for integers The SAT bit
dress up to 64 Kwords of internal memory The ADDRESS
is set to ‘‘1’’ whenever a value read from the accumulator
fields are initialized with the vector operands’ start-address-
cannot be represented within the limits of its data type (e g
es by commands in the command list At the beginning of
16 bits for real and integer and 31 bits for extended real) In
each vector operation the contents of the ADDRESS field
this case the value read from the accumulator will either be
are copied to incrementors Increments can be used by vec-
the maximum allowed value or the minimal allowed value for
tor instructions to step through the corresponding vector
this data type depending on the sign of the accumulator
operands while executing the appropriate calculations
value Note that in some cases when the OVF is set the
There is an address wrap-around for those vector instruc-
SAT will not be set The reason is that if an OVF occurred
tions that require some of their operands to be located in
the value in the accumulator can no longer be used for
cyclic buffers The allowed values for the increment field are
proper SAT detection Upon reset and whenever the
0 through 15 The actual increment will be 2^increment words
ABORT register is written the non reserved bits of the OVF
The allowed values for the WRAP-AROUND field are 0
through 15 The actual wrap-around will be 2^WRAP-AROUND
words The WRAP-AROUND must be greater or equal to
the INCREMENT
The X Y and Z registers can be read and written by the
core These registers can be read and written by the com-
mand-list execution unit as well as by the core when using
SX SXL SXH SY SZ LX LY and LZ instructions
te ^{EABR External Address Base Register}
The format of the external address base register is shown in
Figure 2-7
31
17 16
0
ADDRESS
0
FIGURE 2-7 EABR Register Format
le ^{The EABR register is used together with a 16-bit address}
field to form a 32-bit external address External addresses
are specified as the sum of the value in EABR and two times
the value of the 16-bit address pointed by registers X Y or
Z The only value allowed to be written into bits 0 through 16
of EABR is ‘‘0’’ The EABR register can be read and written
by the core It can also be written by the command-list exe-
o ^{cution unit by using the LEABR instruction}
EABR can hold any value except for FFFE0000 Accessing
external memory with an FFFE0000 in the EABR will cause
unpredictable results
s ^{CLPTR Command List Pointer}
The CLPTR is a 16-bit register that holds the address of the
current command in the internal RAM Writing into the
CLPTR causes the DSPM command-list execution unit to
begin executing commands starting from the address in
b ^{CLPTR The CLPTR can be read and written by the core}
while the command-list execution is idle
Whenever the DSPM command-list execution unit reads a
command from the DSPM RAM the value of CLPTR is up-
dated to contain the address of the next command to be
executed This implies for example that if the last com-
mand in a list is in address N the CLPTR will hold a value of
O ^{N a 1 following the end of command list execution}
register is cleared to ‘‘0’’
The OVF is a read only register It can be read by the core It
can also be read by the command-list execution unit using
the SOVF instruction Reading the OVF by either the core or
the command-list execution unit clears it to ‘‘0’’
PARAM Vector Parameter Register
The format of the PARAM register is shown in Figure 2-9
31
26 25 24 19 18 17 16 15
0
Reserved RND OP SUB CLR COJ LENGTH
FIGURE 2-9 PARAM Register Format
The PARAM register is used to specify the number of itera-
tions and special options for the various instructions The
options are RND OP SUB CLR and COJ The effect of
each of the bits of the PARAM register is specified in Sec-
tion 3 4
The PARAM register can be read and written by the core It
can also be written by the command-list execution unit by
using the LPARAM instruction The value written into PAR-
AM LENGTH must be greater then 0
The value of PARAM LENGTH is not changed during com-
mand-list execution unless it is written into using the
LPARAM instruction
REPEAT Command-List Repeat Register
The format of the repeat register is shown in Figure 2-10
31
16 15
0
COUNT
TARGET
FIGURE 2-10 REPEAT Register Format
The REPEAT register is used together with appropriate
commands to implement loops and branches in the com-
mand list The count is used to specify the number of times
a loop in the command list is to be repeated The target is
used to specify a jump address within the command list
The REPEAT register can be read and written by the core It
can also be read and written by the command-list execution
unit by using SREPEAT and LREPEAT instructions respec-
tively
OVF Overflow Register
The value of REPEAT COUNT changes during the execu-
tion of the DJNZ command
The format of the overflow register is shown in Figure 2-8
ABORT Abort Register
15
21
0
The ABORT register is used to force execution of the com-
Reserved
OVF SAT
mand list to halt Writing any value into this register stops
FIGURE 2-8 OVF Register Format
execution and clears the contents of OVF EXT DSPINT
and DSPMASK The ABORT register can only be written
and only by the core
10