100 HITACHI
Table 8.3
Read Cycle State Description
Read Cycle States
External Memory Space
Internal space
Bits 15–8:
RW7–RW0
WAIT
Pin
Input
Signal
External Memory
Space
DRAM Space
Multi-
Plexed
I/O
On-chip
Peripheral
Module
On-chip
ROM and
RAM
0
Not
sampled
during
read
cycle*
1
Areas 1, 3–5,7: 1
state, fixed
Areas 0, 2, 6: 1 state
+ long wait state
Column add-
ress cycle: 1
state, fixed
(short pitch)
4 states
+ wait
states
from
WAIT
3 states,
fixed
1 state,
fixed
1
Sampled
during
read
cycle
(initial
value)
Areas 1, 3–5, 7: 2
states + wait states
from
WAIT
Areas 0, 2, 6: 1 state
+ long wait state +
wait state from
WAIT
Column
address cycle:
2 states + wait
state from
WAIT
(long
pitch)*
2
Notes: 1. Sampled in the address/data multiplexed I/O space
2. During a CBR refresh, the
WAIT
signal is ignored and the wait state from the RLW1 and
RLW0 bits of RCR is inserted.
Bits 7–2 (reserved): These bits always read as 1. The write value should always be 1.
Bit 1 (wait state control during write (WW1)): WW1 determines the number of states in write
cycles for the DRAM space (area 1) and whether or not to sample the
WAIT
signal. When the
DRAM enable bit (DRAME) of the BCR is set to 1 and area 1 is being used as DRAM space,
clearing WW1 to 0 makes the column address output cycle finish in 1 states (short pitch).
When WW1 is set to 1, it finishes in 2 states plus the wait states from the
WAIT
signal (long
pitch).
Note:
Write 0 to WW1 only when area 1 is used as DRAM space (DRAME bit of BCR is 1).
Never write 0 to WW1 when area 1 is used as external memory space (DRAME is 0).
Bit 1: WW1
DRAM Space (DRAME = 1)
Area 1's External Memory
Space (DRAME = 0)
0
Column address cycle: 1 state (short pitch)
Setting inhibited
2 states + wait state from
WAIT
1
Column address cycle: 2 states + wait state
from
WAIT
(long pitch) (initial value)
Bit 0 (reserved): This bit always reads 1. The write value should always be 1.