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CHAPTER 6 BUS CONTROL FUNCTION
User’s Manual U15109EJ3V0UD
204
6.5 Wait Function
6.5.1 Programmable wait function
To facilitate interfacing with low-speed memories and I/O devices, up to 3 data wait states can be inserted in a bus
cycle that starts every two memory blocks.
The number of wait states can be programmed by using the data wait control register (DWC). Immediately after
the system has been reset, three data wait insertion states are automatically programmed for all memory blocks.
(1) Data wait control register (DWC)
This register can be read/written in 16-bit units.
After reset: FFFFH
R/W
Address: FFFFF060H
Symbol
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
DWC
DW71 DW70 DW61 DW60 DW51 DW50 DW41 DW40 DW31 DW30 DW21 DW20 DW11 DW10 DW01 DW00
DWn1 DWn0
Number of wait states to be inserted
0
0
0
0
1
1
1
0
2
1
1
3
n
Blocks into which wait states are inserted
0
Blocks 0/1
1
Blocks 2/3
2
Blocks 4/5
3
Blocks 6/7
4
Blocks 8/9
5
Blocks 10/11
6
Blocks 12/13
7
Blocks 14/15
Block 0 is reserved for the internal ROM area. It is not subject to programmable wait control, regardless of the
setting of DWC, and is always accessed without wait states.
The internal RAM area of block 15 is not subject to programmable wait control and is always accessed without
wait states. The on-chip peripheral I/O area of this block is also not subject to programmable wait control; wait
control is dependent upon the execution of each peripheral function.