249
10.2.5
Individual Memory Control Register (MCR)
The individual memory control register (MCR) is a 16-bit readable/writable register that specifies
RAS
and
CAS
timing for synchronous DRAM (areas 2 and 3), specifies address multiplexing, and
controls refresh. This enables direct connection of synchronous DRAM without external circuits.
MCR is initialized to H'0000 by a power-on reset, but is not initialized by a manual reset or in
standby mode. Bits TPC1–TPC0, RCD1–RCD0, TRWL1–TRWL0, TRAS1–TRAS0, RASD, and
AMX3–AMX0 are written to in the initialization after a power-on reset and should not then be
modified again. When RFSH and RMODE are written to, write the same values to the other bits.
When using synchronous DRAM, do not access areas 2 and 3 until this register is initialized.
Bit:
15
14
13
12
11
10
9
8
TPC1
TPC0
RCD1
RCD0
TRWL1
TRWL0
TRAS1
TRAS0
Initial value:
0
0
0
0
0
0
0
0
R/W:
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Bit:
7
6
5
4
3
2
1
0
RASD
AMX3
AMX2
AMX1
AMX0
RFSH
RMODE
—
Initial value:
0
0
0
0
0
0
0
0
R/W:
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
Bits 15 and 14—RAS Precharge Time (TPC1, TPC0): When synchronous DRAM interface is
selected as connected memory, they set the minimum number of cycles until output of the next
bank-active command after precharge.
Bit 15: TPC1
Bit 14: TPC0
Description
0
0
1 cycle
(Initial value)
1
2 cycles
1
0
3 cycles
1
4 cycles
Содержание SH7709S
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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 ...
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