Bus Control Register 4 (Bcr4) (Sh7751R Only) - Hitachi SH7751 Hardware Manual

13.2.4

Bus Control Register 4 (BCR4) (SH7751R Only)

Bus control register 4 (BCR4) is a register that enables asynchronous input for pins corresponding
to individual bits.
The BCR4 register is a 32-bit readable/writable register. It is initialized to H'00000000 by a
power-on reset, but is not initialized by a manual reset or in standby mode.
When asynchronous input is set (ASYNCn = 1), the sampling timing is one cycle earlier than
when synchronous input is set (ASYNCn = 0)* (see figure 13.4)
The timings shown in this section and section 23, Electrical Characteristics, are all for the case
where synchronous input is set (ASYNCn = 0).
Note: * With the synchronous input setting, ensure that setup and hold times are observed.
Bit: 31
—
Initial value: 0
R/W: R
Bit: 23
—
Initial value: 0
R/W: R
Bit: 15
—
Initial value: 0
R/W: R
Bit: 7
—
Initial value: 0
R/W: R
Bits 31 to 5—Reserved: These bits are always read as 0, and the write value should always be 0.
30 29 28
— —
0 0
R R
22 21 20
— —
0 0
R R
14 13 12
— —
0 0
R R
6 5
— — ASYNC4 ASYNC3 ASYNC2 ASYNC1 ASYNC0
0 0
R R R/W
27 26
— —
0 0
R R
19 18
— —
0 0
R R
11 10
— —
0 0
R R
4 3
0 0
R/W R/W
Rev. 3.0, 04/02, page 329 of 1064
25 24
— — —
0 0
R R
17 16
— — —
0 0
R R
9
— — —
0 0
R R
2 1
0 0
R/W R/W
0
R
0
R
8
0
R
0
0