SA8702
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1
sames
SA8702
SA8702
02.02.93
BLOCK MODE TIME SLOT ALLOCATION CIRCUIT
Figure 1.
DESCRIPTION
The SA8702 (BMTSAC) is a Block Mode
Time Slot Allocation Circuit. The device is
used to generate 8 consecutive timeslots
in one of 4 blocks in a 32 time-slot PCM
system. Each timeslot pulse is 8 BLCK
cycles long. BCLK is the 2,048 station
clock provided by the system. An active
MRST will disable all outputs until a valid
XSYNC input is recognised. The output
TSX is delayed by half a cycle and indicates
that one of 8 timeslots is currently active.
There are 4 possible modes of operation,
selectable by means of the BL0 and BL1
pins (See Table 1).
APPLICATIONS
s
PCM Switching Systems
s
PCM Transmission Systems
s
Subscriber Multiplex Equipment
s
PBX Systems
PIN CONNECTIONS
All inputs and outputs are C-MOS
compatible. All outputs are push-pull with
the exception of TSX which is open drain.
The inputs MRST and BCLK are Schmitt
Trigger. Inputs BL0 and BL1 have pull-ups.
(See figure 1).
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Table 1.
Input pulse XSYNC occurs periodically in every frame and is used to generate the
first of the eight timeslots and also defines the beginning of Block 0. If XSYNC fails
high then the outputs will be generated as they were before the failure occured.
Should XSYNC fail low then the outputs will be deactivated after completion of the
frame.
Maximum Ratings
All voltages measured with respect to V
SS
.
Parameter
Symbol
Value
Units
Supply voltage
V
DD
+7,5
V
Positive voltage on any pin
V
HM
V
DD
+0,3
V
Negative voltage on any pin
V
LM
V
SS
-0,3
V
Maximum current through any pin
I
HM
10
mA
Storage temperature
T
ST
-55 to +150
C
Operating temperature
T
O
-10 to +70
C
Stresses beyond these values may cause permanent damage to the device. Exposure to
maximum rated conditions for extended periods may affect device reliability.
Operating Modes
BL1
BL0
Mode of Operation
0
0
Outputs active in timeslots 0 to 7
0
1
Outputs active in timeslots 8 to 15
1
0
Outputs active in timeslots 16 to 23
1
1
Outputs active in timeslots 24 to 31
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AC Parameters
Symbol
Min.
Nom.
Max.
Unit
Conditions
XSYNC setup before
T
s
60
-
-
ns
4,75
V
DD
BCLK goes low
5,25
Output propagation
T
pd
-
-
150
ns
4,75
Vdd
delay from active clock
5,25
edge
XSYNC hold time from
T
h
50
-
-
ns
4,75
V
DD
BCLK
5,25
Operating Conditions:
All voltages measured with respect to V
SS
.
Inputs must never be left open.
DC Parameters
Symbol
Min.
Nom.
Max.
Unit Conditions
Supply Voltage
V
DD
4,75
5,00
5,25
V
-
* Input Low Voltage
V
IL
-
-
1,0
V
V
DD
= 5V
* Input High Voltage
V
IH
4,0
-
-
V
V
DD
= 5V
** Output Low Voltage
V
OL
-
-
0,5
V
V
DD
= 5V
I
ol
= 0,5mA
** Output High Voltage
V
OH
4,5
-
-
V
V
DD
= 5V
I
oh
= 0,5mA
Operating Frequency
-
2,048 2,273
MHz
4,75
V
DD
5,25
Operating Temp. range
-10
25
70
C
-
* All inputs are C-MOS level compatible. Pins 6 and 7 have internal pull-up
devices.
** All outputs are push-pull except pin 1 which is open drain.
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PIN DESCRIPTION
Pin No.
I/O
Name
Description
1
O
TSX
An open drain N-channel high impedance, but pulls
low during any active timeslot.
2
I
MRST
A Schmitt trigger input that asynchronously disables
all outputs.
3
O
FSO
A timeslot output which is normally low, and goes
active-high for 8 cycles of BCLK when a valid XSYNC
is made.
4
O
FS1
Similar to pin 3.
5
O
FS2
Similar to pin 3.
6
I
BL0
The input for the LSB of the 2 bit word which defines
the active block.
7
I
BL1
The input for the MSB of the 2 bit word which defines
the active block.
8
I
VSS
The OV ground connection to the device.
9
I
BCLK
The 2,048MHz station clock input.
10
I
XSYNC
The input pulse XSYNC used to generate the first of
the eight timeslots and also defines the beginning of
block 0.
11
O
FS7
Similar to pin 3.
12
O
FS6
Similar to pin 3.
13
O
FS5
Similar to pin 3.
14
O
FS4
Similar to pin 3.
15
O
FS3
Similar to pin 3.
16
I
VDD
The positive supply to the device.
SA8702
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TIMING DIAGRAM
SA8702
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South African Micro-Electronic Systems (Pty) Ltd
P O Box 15888,
33 Eland Street,
Lynn East,
Koedoespoort Industrial Area,
0039
Pretoria,
Republic of South Africa,
Republic of South Africa
Tel:
012 333-6021
Tel:
Int +27 12 333-6021
Fax:
012 333-8071
Fax:
Int +27 12 333-8071
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without the express written consent of SAMES. The information contained herein is current as of the date of
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circuit designed by reference to the information contained herein, will function without errors and as intended by
the designer.
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