Rev.2.00 Oct 16, 2006 page 343 of 354
REJ09B0340-0200
M30245 Group
4. External Buses
4.4.2 Connecting Low-Speed Memory
To connect memory with long access time [ta(A)], either decrease the frequency of BCLK or set a soft-
________
ware wait. Using the RDY feature allows you to connect memory having the timing that precludes con-
nection though you set software wait.
(1) Using software wait
Set software wait for the external memory areas by using either of bits CS0W through CS3W of the
chip select control register (address 0008
16
) or the chip select expansion register (address 001B
16
).
________
When using the RDY signal, the corresponding CS0W through CS3W bit must be set to “0”.
Bits CS0W through CS3W of the chip select control register correspond to chip select CS0 through
CS3, respectively. If these bits are set to “1”, the read bus cycle results in one cycle of BCLK and the
write bus cycle results in two cycles of BCLK; if these bits are set to “0”, the read/write cycle results in
two, three, or four cycles of BCLK according to the chip select expansion register setting. When the
corresponding bit of the chip select control register is set to “0”, the chip select expansion register
setting becomes valid. When this bit is set to “1”, set the corresponding bit of the chip select expansion
register to “00
2
”.
When reset, the value of the chip select control register and the chip select expansion register is set to
“00
16
”.
These control bits do not affect the SFR area and the internal ROM/RAM area.
Figure 4.4.1 shows software wait and bus cycle, and Figure 4.4.3 shows relation of processor mode
and the wait bit (CSiW, CSiEW).
Table 4.4.1. Software waits and bus cycles
Area
SFR
Internal ROM/RAM
External memory
areas
CSxW
(Note 2)
Invalid
Invalid
0
0
0
0
1
CSExW
(Note 2)
Invalid
Invalid
00
01
10
11
00
Read
2 BCLK cycles
1 BCLK cycle
2 BCLK cycles
3 BCLK cycles
4 BCLK cycles
Write
2 BCLK cycles
1 BCLK cycle
2 BCLK cycles
3 BCLK cycles
4 BCLK cycles
Bus Cycles
_______
Note 1: When using the RDY signal, set to “0”.
Note 2: Set CSEiW bits (i = 0 to 3) after setting the corresponding CSiW bit (i = 0 to 3) of the CSR register
to “0”. When CSiW bits are set to “1”, CSEiW bits must be returned to “00
2
”.
Do not set
1 BCLK cycle
2 BCLK cycles
Содержание M16C FAMILY
Страница 12: ...Chapter 1 Hardware...
Страница 13: ...See M30245 group datasheet...
Страница 14: ...Chapter 2 Peripheral Functions Usage...
Страница 303: ...THIS PAGE IS BLANK FOR REASONS OF LAYOUT...
Страница 304: ...Chapter 3 Examples of Peripheral Functions Applications...
Страница 340: ...Chapter 4 External Buses...
Страница 361: ...THIS PAGE IS BLANK FOR REASONS OF LAYOUT...
Страница 362: ...Chapter 5 Standard Characteristics...
Страница 369: ...1753 Shimonumabe Nakahara ku Kawasaki shi Kanagawa 211 8668 Japan M30245 Group REJ09B0340 0200 User s Manual...