27
T bit: The T bit in the status register (SR) is used to indicate the result of compare operations, and
is read as a TRUE/FALSE condition determining if a conditional branch is taken or not. To
improve processing speed, the T bit logic state is modified only by specific operations. An
example of how the T bit may be used in a sequence of operations is shown below.
ADD
#1, R0
;T bit not modified by ADD operation
CMP/EQ
R1, R0
;T bit set to 1 when R0
=
0
BT
TRGET
;branch taken to TRGET when T bit = 1 (R0 = 0)
Literals: Byte-length literals are inserted directly into the instruction code as immediate data. To
maintain the 16-bit fixed-length instruction code, word or longword literals are stored in a table in
main memory rather than inserted directly into the instruction code. The memory table is accessed
by the MOV instruction using PC-relative addressing with displacement, as follows:
MOV.W
@(disp, PC), R0
Absolute Addresses: As with word and longword literals, absolute addresses must also be stored
in a table in main memory. The value of the absolute address is transferred to a register and the
operand access is specified by indexed register-indirect addressing, with the absolute address
loaded (like word and longword immediate data) during instruction execution.
16-Bit and 32-Bit Displacements: In the same way, 16-bit and 32-bit displacements also must be
stored in a table in main memory. Exactly like absolute addresses, the displacement value is
transferred to a register and the operand access is specified by indexed register-indirect addressing,
loading the displacement (like word and longword immediate data) during instruction execution.
Содержание SH7709S
Страница 2: ...Hitachi SuperH RISC engine SH7709S Hardware Manual ADE 602 250 Rev 1 0 09 21 01 Hitachi Ltd ...
Страница 75: ...56 ...
Страница 107: ...88 ...
Страница 125: ...106 ...
Страница 139: ...120 ...
Страница 203: ...184 ...
Страница 245: ...226 ...
Страница 292: ...273 T1 CKIO A25 to A0 CSn RD WR RD D31 to D0 WEn D31 to D0 BS T2 Read Write Figure 10 6 Basic Timing of Basic Interface ...
Страница 323: ...304 Tp TRr TRrw TRrw CKIO CKE CSn RAS3U RAS3L CASU CASL RD WR Figure 10 28 Synchronous DRAM Auto Refresh Timing ...
Страница 411: ...392 ...
Страница 609: ...590 ...
Страница 635: ...616 ...
Страница 663: ...644 ...
Страница 679: ...660 ...