SAB 82532/SAF 82532
Serial Interface (layer-1 functions)
Semiconductor Group
85
07.96
Note 2: Restrictions for frequency ratios between receive frequency (
f
r
), transmit
frequency (
f
x
) and master clock frequency (
f
m
):
Normal mode; clock mode 0, 2a, and 6a:
Master clock mode:
There are no restrictions on the relative phases of the clocks. The conditions
are valid independent of strobe signals or time-slot widths: i.e. in normal mode
clock mode 1 always fulfills the condition, irrespective of how receive and
transmit data are strobed. Thus, by using strobes the above condition may
always be fulfilled irrespective of the net data rates.
f
r
/
f
x
<
3
1)
f
m
/
f
x
≥
2.5;
f
r
/
f
m
<
3
1
)
.
Note 3: Restrictions for frequency ratios between receive frequency (f
r
), transmit
frequency (f
x
) and master clock frequency (f
m
):
Master clock mode:
f
r
/
f
m
<
3
1
)
Non bus configuration:
In addition: For a given transmit clock f
x
a master clock f
m
with at least 1.25 f
m
periods in the low phase of transmit clock f
x
has to be provided.
f
m
/
f
x
>
2.5
Bus configuration:
In addition: For a given transmit clock f
x
a master clock f
m
with at least 2.5 f
m
periods in the low phase of transmit clock f
x
has to be provided.
Example 1: f
x
= 2 MHz with low/high ratio of 0.25/0.75 => f
m
= 20 MHz
(see
figure 37
)
Example 2: f
x
= 4 MHz with low/high ratio of 0.75/0.25 => f
m
= 13.32 MHz
(see
figure 38
)
f
m
/
f
x
>
5
Generally, in master clock mode the low/high ratio of transmit clock should be
in the range 0.25/0.75 .. 0.75/0.25.
There are no restrictions on the relative phases of the clocks. The conditions
are valid independent of strobe signals or time-slot widths: i.e. in normal mode
clock mode 1 always fulfills the condition, irrespective of how receive and
transmit data are strobed. Thus, by using strobes the above condition may
always be fulfilled irrespective of the net data rates.
1)
Reduced to 1.5 if receive address is pushed to RFIFO in HDLC/SDLC mode.