peb20550 Infineon Technologies Corporation, peb20550 Datasheet - Page 139

• Manufacturer Part Number: peb20550
• Description: Extended Pcm Interface Controller
• Manufacturer: Infineon Technologies Corporation

5.3.3.2 Access to the Data Memory Code (Tristate) Field
The data memory code field exists only for the upstream DM block and is also called the
PCM tristate field. Each (sub)time slot of each PCM transmit port can be individually
tristated via these code field locations.
If a (sub)time slot is set to low impedance, the contents of the corresponding DM data
field location is transmitted with a push-pull driver onto the transmit port TxD# and the
tristate control line TSC# is pulled low for the duration of that (sub)time slot.
If a (sub)time slot is set to high impedance, the transmit port TxD# will be tristated and
the TSC# line is pulled high for the duration of that (sub)time slot.
There are 4 code bits for selecting the tristate function of each 8 bit time slot i.e. 1 control
bit for each 16 kbit/s (2 bits) subtime slot. If a control bit is set to 1, the corresponding
subtime slot is set to low impedance, if it is set to 0 the subtime slot is tristated.
Figure 50 illustrates this behavior.
Figure 50
Tristate Control at the PCM Interface
The tristate field can be written to and, for test purposes, also be read back.
There are two commands (Memory Operation Codes) for accessing the tristate field:
With the “Single Channel Tristate Control” command (MOC3 … 0 = 1100) the tristate
field of a single PCM time slot can be written to and also read back. The 4 least
significant bits of MADR are exchanged with the code field of the time slot selected by
the MAAR register.
With the “Tristate Control Reset” command (MOC3 … 0 = 1101) the tristate field of all
PCM time slots can be written to with a single command. The 4 bits of MADR are then
copied to all code field locations regardless of the address programmed to MAAR. Such
a complete access to the DM tristate field takes 1035 RCL cycles.
Semiconductor Group
PCM Time-Slot#
DM Data Field
DM Tristate Field
TxD#
TSC#
High Z
1 -
0 -
1 -
0 -
X X X X 0 1 1 0
0
0
N
1
1
X
0
X
1
1
1
N+1
X
139
0
X
0
1
1
X
0
X
X
0
N+2
X
X
0
X
X
0
X
1
1
0
Application Hints
1
1
1
N+3
0
1
PEB 2055
0
PEF 2055
ITD08065
1
1
0