Chapter 5 External Bus Interface (S12XEBIV4)
MC9S12XE-Family Reference Manual Rev. 1.19
Freescale Semiconductor
251
The resulting timing pattern of the external bus signals is outlined in the following tables for read, write
and interleaved read/write accesses. Three examples represent different access lengths of 1, 2, and n–1 bus
cycles. Non-shaded bold entries denote all values related to Access #0.
The following terminology is used:
‘addr’ — value(ADDRx); small letters denote the logic values at the respective pins
‘x’ — Undefined output pin values
‘z’ — Tristate pins
‘?’ — Dependent on previous access (read or write); IVDx: ‘ivd’ or ‘x’; DATAx: ‘data’ or ‘z’
5.4.2.4.1
Read Access Timing
Table 5-12. Read Access (1 Cycle)
Access #0
Access #1
Bus cycle ->
...
1
2
3
...
ECLK phase
...
high
low
high
low
high
low
...
ADDR[22:20] / ACC[2:0]
...
addr 0
acc 0
addr 1
acc 1
addr 2
acc 2
...
ADDR[19:16] / IQSTAT[3:0] ...
iqstat -1
iqstat 0
iqstat 1
...
ADDR[15:0] / IVD[15:0]
...
?
ivd 0
ivd 1
...
DATA[15:0] (internal read)
...
?
z
z
z
z
z
...
DATA[15:0] (external read)
...
?
z
data 0
z
data 1
z
...
RW
...
1
1
1
1
1
1
...
Table 5-13. Read Access (2 Cycles)
Access #0
Access #1
Bus cycle ->
...
1
2
3
...
ECLK phase
...
high
low
high
low
high
low
...
ADDR[22:20] / ACC[2:0]
...
addr 0
acc 0
addr 0
000
addr 1
acc 1
...
ADDR[19:16] / IQSTAT[3:0] ...
iqstat-1
iqstat 0
0000
...
ADDR[15:0] / IVD[15:0]
...
?
x
ivd 0
...
DATA[15:0] (internal read)
...
?
z
z
z
z
z
...
DATA[15:0] (external read)
...
?
z
z
z
data 0
z
...
RW
...
1
1
1
1
1
1
...
Table 5-14. Read Access (n–1 Cycles)
Access #0
Access #1
Bus cycle ->
...
1
2
3
...
n
...
ECLK phase
...
high
low
high
low
high
low
...
high
low
...
ADDR[22:20] / ACC[2:0]
...
addr 0
acc 0
addr 0
000
addr 0
000
...
addr 1
acc 1
...
ADDR[19:16] / IQSTAT[3:0] ...
iqstat-1
iqstat 0
0000
...
0000
...
ADDR[15:0] / IVD[15:0]
...
?
x
x
...
ivd 0
...
DATA[15:0] (internal read)
...
?
z
z
z
z
z
...
z
z
...
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages
