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Table 2.3
Delayed Branch Instructions
SH7040 Series CPU
Description
Example of Conventional CPU
BRA
TRGET
ADD
R1,R0
Executes an ADD before
branching to TRGET
ADD.W
R1,R0
BRA
TRGET
Multiplication/Accumulation Operation: 16-bit
×
16-bit
→
32-bit multiplication operations are
executed in one to two cycles. 16-bit
×
16-bit + 64-bit
→
64-bit multiplication/accumulation
operations are executed in two to three cycles. 32-bit
×
32-bit
→
64-bit and 32-bit
×
32-bit + 64-
bit
→
64-bit multiplication/accumulation operations are executed in two to four cycles.
T Bit: The T bit in the status register changes according to the result of the comparison, and in
turn is the condition (true/false) that determines if the program will branch. The number of
instructions that change the T bit is kept to a minimum to improve the processing speed (table
2.4).
Table 2.4
T Bit
SH7040 Series CPU
Description
Example of Conventional CPU
CMP/GE
R1,R0
BT
TRGET0
BF
TRGET1
T bit is set when R0
≥
R1. The
program branches to TRGET0
when R0
≥
R1 and to TRGET1
when R0 < R1.
CMP.W
R1,R0
BGE
TRGET0
BLT
TRGET1
ADD
#1,R0
CMP/EQ
#0,R0
BT
TRGET
T bit is not changed by ADD. T bit is
set when R0 = 0. The program
branches if R0 = 0.
SUB.W
#1,R0
BEQ
TRGET
Immediate Data: Byte (8-bit) immediate data resides in instruction code. Word or longword
immediate data is not input via instruction codes but is stored in a memory table. An immediate
data transfer instruction (MOV) accesses the memory table using the PC relative addressing mode
with displacement (table 2.5).
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