m30833fjgp Renesas Electronics Corporation., m30833fjgp Datasheet - Page 384

• Manufacturer Part Number: m30833fjgp
• Description: Renesas 16/32-bit Single-chip Microcomputer M16c Family / M32c/80 Series
• Manufacturer: Renesas Electronics Corporation.

R
R
M
23.1 DRAMC Multiplexed Address Output
23.2 Refresh
e
E
3
. v
J
2
0
DRAMC is not available when the PM11 to PM10 bits in the PM1 register are set to "11
PM11 to PM10 bits to "00
the PM02 bit in the PM0 register to "1" (RD/WRH/WRL).
Required wait time between DRAM power-on and memory operation, and necessary processing of dummy
cycle for refresh varies with externally attached DRAM specifications.
DRAMC outputs signals, which are multiplexed row addresses and column addresses, to address bus A
A
23.2.1 Refresh
23.2.2 Self-Refresh
1
C
9
3 .
B
20
Refresh method is the CAS-before-RAS refresh. The REFCNT register controls the refresh interval. Re-
fresh signals are not output in a hold state.
The setting value of the REFCNT register is obtained as follows:
The value of the REFCNT register (00
The refresh signal described in 23.2.1 stops while the CPU stops in stop mode, etc. The DRAM self-
refresh function can be activated by setting the self-refresh before the CPU stops. Setting and cancella-
tion procedures for the self-refresh are as follows:
(1) Setting self-refresh (with 1 wait state, 4 Mbytes)
(2) Cancellation of self-refresh (with 1 wait state, 4M bytes)
Both RAS and CAS are held "L" during self-refresh. When devices other than DRAM are attached, the
______
WR signal is held "L". Take procedures such as applying an "H" signal to the CS.
Figures 23.3 to 23.5 show bus timings during DRAM access.
8 /
0
1
. Figure 23.2 shows an output format for multiplexed addresses.
3
0
3
J
G
4
a
_______
0 -
n
o r
•••
mov.b
mov.b
nop
nop
•••
•••
mov.b
mov.b
mov.b
•••
3 .
1
u
, 1
3
p
1
2
(
M
0
;Execute the nop instruction twice
;
0
3
6
2
#00000001b,DRAMCONT
#10001011b,DRAMCONT
#00000001b,DRAMCONT
#00001011b,DRAMCONT
400h, 400h
_______
C
Page 361
8 /
, 3
M
_______
2
3
," "01
2
C
f o
8 /
4
2
3
8
" or "10
) T
8
_______
16
2
____ ________ ________
" (mode 0 to 2). When the 16-bit DRAM data bus is selected, set
to FF
;Set the AR2 to AR0 bits to "000
;Set the AR2 to AR0 bits again and the SREF bit to "1"
;Set the AR2 to 0 bits to "000
;Set the AR2 to AR0 bits again
;DRAM access is disabled immediately after cancellation.
This is an example of a dummy read operation.
(self-refresh on) simultaneously
and the SREF bit to "0" (DRAM disabled) simultaneously
16
) = refresh interval time / (CPU clock frequency X 32) - 1
2
" (self-refresh cancellation)
2
_____
" (DRAM disabled)
2
" (mode 3). Set the
23. DRAMC
8
to