
328
10.3.10
MCS[0]
to
MCS[7]
Pin Control
The SH7709S is provided with pins
MCS[0]
–
MCS[7]
as dedicated
CS
pins for the ROM
connected to area 0 or 2. Assertion of
MCS[0]
–
MCS[7]
is controlled by settings in MCSCR0–
MCSCR7. This enables 32-, 64-, 128-, or 256-Mbit memory to be connected to area 0 or area 2.
Table 10.15 shows MCSCR0–MCSCR7 settings and
MCS[0]
–
MCS[7]
assertion conditions.
As the
MCS[0]
–
MCS[7]
pins are multiplexed as the PTC0–PTC7 pins, when using these pins as
MCS[0]
–
MCS[7]
, the corresponding bits in the PCCR register should be set to “other function.”
When CS2/0 = 0 in the MCSCR0 and when the PTC0 pin is switched to
MCS[0]
(when
PCOMD1–PCOMD0 are set to “other function”), the
CS0
pin is also switched to
MCS[0]
.
As port register writes operate on the peripheral clock, they take time compared with instruction
execution by the CPU operating on the high-speed internal clock. Therefore, if an instruction that
accesses
MCS[1]
to
MCS[7]
is located several instructions after an instruction that switches port C
to
MCS
, the switch from PTC[n] to
MCSn
and from
CS0
to
MCS[0]
may not be performed
correctly.
To prevent this problem, the following switching procedure should be used.
•
When the program runs with cache on
(1) To switch port C to
MCS
, set the corresponding bits in the PCCR register to 00 ("other
function").
(2) Read the PCCR register and check whether the set value is read. Repeat until the set value is
read.
(3) Perform a dummy read from non-cacheable CS0 space (e.g. address H'A0000000). This will
result in an access to the CS0 space, and immediately afterward, CS0 will be switched to
MCS[0]
, and port C[n] will be switched to
MCS[n]
.
(4) Access can now be made to the
MCS[1]
to
MCS[7]
spaces.
•
When the program runs in
MCS[0]
space with cache off
(1) Set the PCCR register as in (1) above.
(2) Place at least three NOP instructions after the instruction in (1). As a result, when the PCCR
register is rewritten, an access to the CS0 space will be generated, and immediately afterward,
CS0 will be switched to
MCS[0]
, and port C[n] will be switched to
MCS[n]
.
(3) Access can now be made to the
MCS[1]
to
MCS[7]
spaces.
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 ...