Fujitsu FR81S User Manual
CHAPTER 36: EXTERNAL BUS INTERFACE
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : EXTERNAL BUS INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
37
Table 5-8 Address/Data split bus timing parameters
Parameter name
Function name
Description
ASCY(ASX CYcle)
ASX output extension cycle
count
"L" is output to ASX for (ASCY+1) cycles
from when the access starts.
ACS[1:0]
(A00 to A21 to CSnX
delay cycle)
A00 to A21 → CSnX delay
cycle count
Output of "L" to CSnX (n=0 to 3) starts after
the ACS count has finished from ASX output.
CSRD[1:0]
(CSnX to RDX setup cycle)
CSnX → RDX setup cycle
During read access, output of "L" to RDX
begins after the CSRD count finishes after
"L" output to CSnX begins.
RWT[3:0]
(Read access auto WaiT)
Read access auto wait
During read access, the RDX output returns to "H"
after (RWT+1) count from when output of "L" to
RDX begins.
after (RWT+1) count from when output of "L" to
RDX begins.
RDCS[1:0]
(RDX to CSnX hold cycle)
RDX → CSnX hold cycle
During read access, the output of CSnX returns to
"H" after RDCS count from the cycle where the
output of RDX returns to "H".
"H" after RDCS count from the cycle where the
output of RDX returns to "H".
CSWR[1:0]
(CSnX to WRnX setup
cycle)
CSnX → WRnX setup cycle
During write access, output of "L" to WRnX
begins after the CSWR count finishes after "L"
output to CSnX begins.
WWT[3:0]
(Write access auto WaiT)
Write access auto wait
During write access, the output to WRnX (n=0, 1)
returns to "H" after (WWT+1) count finishes.
returns to "H" after (WWT+1) count finishes.
WRCS[1:0]
(WRnX to CSnX hold
cycle)
WRnX → CSnX hold cycle
During write access, the output of CSnX returns to
"H" after WRCS count from the cycle where the
output of WRnX returns to "H".
RIDL[1:0]
(Read access IDLe cycle)
Read access idle cycle
After a read access has finished, the next access is
able to start after RIDL count has finished.
WRCV[1:0]
(Write ReCoVery cycle)
Write recovery cycle
After a write access has finished, the next access is
able to start after WRCV count has finished.
The number of access cycles is determined from the following formula.
Number of read access cycles = Address & data output (1) + ACS (0 to 3) + CSRD (0 to 3) + RWT (0 to
15) +RDCS (0 to 3)
Minimum: 1 cycle; Maximum: 25 cycles
Number of write access cycles = Address & data output (1) + ACS (0 to 3) + CSWR (0 to 3) + WWT (0 to
15) + WRCS (0 to 3)
Minimum: 1 cycle; Maximum: 25 cycles
The following conditions need to be met in order to correctly establish the protocol.
ASCY
≤
ACS + CSRD + RWT + RDCS and ASCY
≤
ACS + CSWR + WWT + WRCS
MB91520 Series
MN705-00010-1v0-E
1236