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Enhanced Time Processing Unit (eTPU2)
MPC5644A Microcontroller Reference Manual, Rev. 6
934
Freescale Semiconductor
Microinstructions with fields ABSE and ABDE
In microinstructions where ABSE and ABDE fields are available (1 bit each), ABSE controls register set
selection for T4ABS and ABDE controls register set selection for T2ABD.
shows the
meaning of values for ABSE and ABDE fields.
Microinstructions Without Fields ABSE and ABDE
When ABSE and ABDE are not available in a microinstruction format, register set is selected by T4BBS
field.
explains how to select a register set either for T4ABS and T2ABD.
24.5.9.2.2
Selecting sources and destination
All ALU/MDU operations need two sources (called AS and BS) and one destination (called AD), except
for some of those that use immediate data (see
Section 24.5.9.2.11, Operations with immediate data
).
Fields T4ABS (4 bits), ABSE (1 bit), T4BBS (3 bits) select sources, while T2ABD (4 bits) and ABDE (1
bit) select the destination. When MDU is used (multiply/divide), T2ABD destination selection is ignored
and results are stored in MACH and MACL (see
Section 24.5.8.3, MAC and Divide Unit (MDU)
and ABDE are not available in some microinstruction formats that support ALU/MDU operations.
However, in all formats where ABSE is available, ABDE is also available and vice-versa. The existence
of ABSE/ABDE fields changes the meaning of T4BBS field, as shown in
. On instructions
with immediate data, it is used as B-source (see
Section 24.5.9.2.11, Operations with immediate data
All sources and destinations have a size associated to them, and these sizes are used to select flag sample
position (see
Section 24.5.9.2.3, Flags sampling control
). Sizes can be 8, 16 or 24 bits. Registers that are
not exactly of one of these sizes are treated as the immediately upper size (e.g., CHAN[4:0] is an 8-bit
source). See
Section 24.5.9.2.3, Flags sampling control
, for more information.
Table 24-78. Register Set Selection by ABSE or ABDE
ABSE or ABDE
Register set selected
0
second
1
first
Table 24-79. Register set selection by T4BBS w/o ABSE, ABDE
T4BBS
Register set for T2ABD
Register set for T4ABS
0xx
first
first
100
second
second
101
second
first
110
first
second
111
first
first
none
1
1
Refers to operations with immediate data as B-source, without ABSE, ABDE.
first
first
Summary of Contents for MPC5644A
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Page 56: ...Memory Map MPC5644A Microcontroller Reference Manual Rev 6 56 Freescale Semiconductor...
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