CHAPTER 4 BUS CONTROL FUNCTION
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User’s Manual U14359EJ4V0UM
4.6.4 Bus cycles in which wait function is valid
In the V850E/MA1, the number of waits can be specified according to the memory type specified for each memory
block. The following shows the bus cycles in which the wait function is valid and the registers used for wait setting.
Table 4-1. Bus Cycles in Which Wait Function Is Valid
Programmable Wait Setting
Bus Cycle
Type of Wait
Register
Bit
Wait
Count
Wait from
WAIT pin
Address setup wait
ASC
ACn1, ACn0
0 to 3
−
(invalid)
SRAM, external ROM, external I/O
cycles
Data access wait
DWC0, DWC1
DWn2 to DWn0
0 to 7
√
(valid)
Address setup wait
ASC
ACn1, ACn0
0 to 3
−
(invalid)
Off-page
Data access wait
DWC0, DWC1
DWn2 to DWn0
0 to 7
√
(valid)
Page ROM cycle
On-page
Data access wait
PRC
PRW2 to PRW0
0 to 7
√
(valid)
RAS precharge
SCRm
RPC1m, RPC0m
1 to 3
−
(invalid)
Row address hold
SCRm
RHC1m, RHC0m
0 to 3
−
(invalid)
Off-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
−
(invalid)
CAS precharge
SCRm
CPC1m, CPC0m
0 to 3
−
(invalid)
Read access
On-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
−
(invalid)
RAS precharge
SCRm
RPC1m, RPC0m
1 to 3
−
(invalid)
Row address hold
SCRm
RHC1m, RHC0m
0 to 3
−
(invalid)
Off-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
−
(invalid)
CAS precharge
SCRm
CPC1m, CPC0m
1 to 3
−
(invalid)
Write access
On-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
−
(invalid)
RAS precharge
RWC
RRW1, RRW0
0 to 3
−
(invalid)
CBR refresh cycle
RAS active width
RWC
RCW2 to RCW0
1 to 7
−
(invalid)
RAS precharge
RWC
RRW1, RRW0
0 to 3
−
(invalid)
RAS active width
RWC
RCW2 to RCW0
1 to 7
−
(invalid)
EDO DRAM
cycle
CBR self-refresh cycle
Self-refresh release width
RWC
SRW2 to SRW0
0 to 7
−
(invalid)
SDRAM cycle
Row address precharge
SCRm
BCW1m,
BCW0m
1 to 3
−
(invalid)
External I/O
→
SRAM
Data access wait
DWC0, DWC1
DWn2 to DWn0
0 to 7
√
(valid)
RAS precharge
SCRm
RPC1m, RPC0m
1 to 3
−
(invalid)
Row address hold
SCRm
RHC1m, RHC0m
0 to 3
−
(invalid)
Off-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
√
(valid)
CAS precharge
SCRm
CPC1m, CPC0m
0 to 3
−
(invalid)
DRAM
→
external I/O
On-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
√
(valid)
RAS precharge
SCRm
RPC1m, RPC0m
1 to 3
−
(invalid)
Row address hold
SCRm
RHC1m, RHC0m
0 to 3
√
(valid)
Off-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
−
(invalid)
CAS precharge
SCRm
CPC1m, CPC0m
1 to 3
√
(valid)
DMA flyby
transfer
cycle
External I/O
→
DRAM
On-page
Data access wait
SCRm
DAC1m, DAC0m
0 to 3
−
(invalid)
Remark
n = 0 to 7, m = 1, 3, 4, 6