DS89C430 Maxim, DS89C430 Datasheet - Page 33

• Manufacturer Part Number: DS89C430
• Description: The DS89C430 and DS89C450 offer the highest performance available in 8051-compatible microcontrollers
• Manufacturer: Maxim

Table 10. Page Mode 2, Data Memory Cycle Stretch Values (PAGES1:PAGES0 = 11)
As shown in the previous tables, the stretch feature supports eight stretched external data-memory access options,
which can be categorized into three timing groups. When the stretch value is cleared to 000b, there is no stretch on
external data memory access, and a MOVX instruction is completed in two basic memory cycles. When the stretch
value is set to 1, 2, or 3, the external data memory access is extended by 1, 2, or 3 stretch memory cycles,
respectively. Note that the first stretch value does not result in adding four system clocks to the control signals. This
is because the first stretch uses one system clock to create additional address setup and data bus float time and
one system clock to create additional address and data hold time. When using very slow RAM and peripherals, a
larger stretch value (4–7) can be selected. In this stretch category, two stretch cycles are used to create additional
setup (the ALE pulse width is also stretched by one stretch cycle for page miss) and one stretch cycle is used to
create additional hold time. The following timing diagrams illustrate the external data memory access at divide-by-1
system clock mode (CD1:CD0 = 10b).
Figure 12
PAGES1:PAGES0 = 01. The stretch cycle shown is for a stretch value of 1 and is coincident with a page miss.
Note that the first stretch value does not result in adding four system clocks to the RD/WR control signals. This is
because the first stretch uses one system clock to create additional setup and one system clock to create
additional hold time.
Figure 13
memory cycle is shorter than a page miss data memory cycle. The ALE pulse width is also stretched by a stretch
cycle in the case of a page miss.
The stretched data memory bus cycle timing relationship for PAGES = 11 is identical to nonpage mode operation
since the basic data memory cycle always contains four system clocks in this page mode operation.
MD2:MD0
000
001
010
011
100
101
110
111
shows the timing relationship for a slow peripheral interface (stretch value = 4). Note that a page hit data
illustrates the external data-memory stretch-cycle timing relationship when PAGEE = 1 and
STRETCH
CYCLES
10
0
1
2
3
7
8
9
4X/ 2X , CD1,
CD0 = 100
0.5
RD/WR PULSE WIDTH (IN NUMBER OF OSCILLATOR CLOCKS)
1
2
3
4
5
6
7
DS89C430/DS89C450 Ultra-High-Speed Flash Microcontrollers
4X/ 2X , CD1,
CD0 = 000
33 of 46
10
12
14
1
2
4
6
8
4X/ 2X , CD1,
CD0 = X10
12
16
20
24
28
2
4
8
4X/ 2X , CD1,
CD0 = X11
12,288
16,384
20,480
24,576
28,672
2048
4096
8192