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M30245 Group
C h i p s e l e c t c o n t r o l r e g i s t e r
b 7
b 6
b 5
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Chip select expansion register
b 7
b 6
b 5
Figure 4.2.3. Level of BYTE pin and external data bus width
4.2.3 R/W Modes
The read/write signal that is output when accessing an external area can be selected between the RD/
________ ______
BHE/WR and the RD/WRH/WRL modes by setting the R/W mode select bit (bit 2) of the processor mode
register 0 (address 0004
_____ _________ ________
the (RD/WRH/WRL) to access a 16-bit wide RAM.
When the M30245 is reset, the RD/BHE/WR mode is selected by default. To switch over the R/W mode,
change the RD/BHE/WR to the RD/WRH/WRL mode before accessing an external RAM.
Refer to the connection examples of RD/BHE/WR and RD/WRH/WRL shown in Section 4.3, "Connection
Examples."
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
b 4
b 3
b 2
b 1
b 0
S y m b o l
C S R
B i t s y m b o l
C S 0
C S 1
C S 2
C S 3
C S 0 W
CS1W
CS2W
C S 3 W
b 4
b 3
b 2
b 1
b 0
Symbol
CSE
B i t s y m b o l
CSE0W
C S E 1 W
C S E 2 W
C S E 3 W
N o t e 1 : S e t C S E i W b i t s ( i = 0 t o 3 ) a f t e r s e t t i n g t h e c o r r e s p o n d i n g C S i W b i t ( i = 0 t o 3 ) o f t h e C S R
r e g i s t e r t o " 0 " . W h e n C S i W b i t s a r e s e t t o " 1 " , C S E i W b i t s m u s t b e r e t u r n e d t o " 0 0
_____ _________ ________
). Use the (RD/BHE/WR) mode to access an 8-bit and a 16-bit wide RAM, and
16
_____ ________ ______
_____ _______ ______
_____ _________ ________
page 333 of 354
A d d r e s s
0 0 0 8
1 6
B i t n a m e
C S 0 o u t p u t e n a b l e b i t
C S 1 o u t p u t e n a b l e b i t
C S 2 o u t p u t e n a b l e b i t
C S 3 o u t p u t e n a b l e b i t
C S 0 w a i t b i t
C S 1 w a i t b i t
CS2 wait bit
CS3 wait bit
Address
001B
16
B i t n a m e
CS0 wait expansion bit
C S 1 w a i t e x p a n s i o n b i t
C S 2 w a i t e x p a n s i o n b i t
CS3 wait expansion bit
_____ ________ ______
_____ ________ ______
_____ _________ ________
4. External Buses
W h e n r e s e t
0 1
1 6
Function
0 : C h i p s e l e c t o u t p u t d i s a b l e d
( N o r m a l p o r t p i n )
1 : C h i p s e l e c t o u t p u t e n a b l e d
0 : W a i t s t a t e i n s e r t e d
1 : N o w a i t s t a t e
When reset
00
16
F u n c t i o n
0 0 : 1 W a i t s t a t e
0 1 : 2 W a i t s t a t e s
1 0 : 3 W a i t s t a t e s
1 1 : I n h i b i t e d
R W
R W
".
2
_____
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