RX610 Group
11. Buses
R01UH0032EJ0120 Rev.1.20
Page 293 of 1006
Feb 20, 2013
11.5.2
External Wait Function
Wait cycles can be extended by the WAIT# signal over the length of normal access cycle wait (specified by the
CSRWAIT[4:0] and CSWWAIT[4:0] bits in CSiWCNT1) and page access cycle wait (specified by the CSPRWAIT[2:0]
and CSPWWAIT[2:0] bits in CSiWCNT1).
When external wait is enabled (the EWENB bit = 1 in CSiMOD), wait cycles are inserted while the WAIT# signal is held
low. When external wait is disabled (the EWENB bit = 0 in CSiMOD), the WAIT# signal has no effect.
All wait cycles specified in CSiWCNT1 are inserted independently of the WAIT# signal.
11.5.2.1
Normal Access
Sampling of the WAIT# signal begins upon completion of the wait cycle (Tend) specified in CSiWCNT1. The bus cycle
is extended while the WAIT# signal is held low. The wait cycle ends (Tend) at the next cycle after the WAIT# signal
becomes high.
11.5.2.2
Page Access
The first data read or data write operation is the same as the normal read or write operation. Sampling of the WAIT#
signal begins upon completion of the wait cycle (Tend) specified in the CSiWCNT1 register. The bus cycle is extended
while the WAIT# signal is held low. The wait cycle ends (Tend) at the next cycle after the WAIT# signal becomes high.
With respect to the second and subsequent read accesses, sampling of the WAIT# signal begins upon completion of the
wait cycle of the page access. The wait cycle of the page access is extended while the WAIT# signal is held low, and
ends (Tend) at the next cycle after the WAIT# signal becomes high.
D0
D1
A1
A0
Page read cycle wait (CSPRWAIT)
External wait
External wait
Read cycle wait (CSRWAIT)
Tw1
Tpw1
Tpwn
Tw2
Tend
Tend
Twn (Tend)
(Tend)
Th
Data write
(WR0#, WR1#, WR#)
External wait
(WAIT#)
Data bus
(D15 to D0)
External bus clock
(BCLK)
Address
(A23 to A0)
Chip select/byte control
(CSin/BC0#, BC1#)
[Legend] n = 0 to 7
Data read
(RD#)
Figure 11.19 Example of External Wait Timing (Page-Read Access to 16-Bit Bus Space)