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TP3155 Fiches technique(PDF) 5 Page - National Semiconductor (TI) |
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TP3155 Fiches technique(HTML) 5 Page - National Semiconductor (TI) |
5 / 10 page Functional Description OPERATING MODES The TP3155 control interface requires an 8-bit serial control word which is compatible with the TP3020TP3021 and 29102911 CODECs Two bits X and R define which of the two groups of frame sync outputs FSX0toFSX3orFSR0to FSR3 is affected by the control word and a 6-bit assign- ment field specifies the selected time slot from 0 to 31 A frame sync output is active-high for one time slot which is always 8 cycles of BCLK A frame may consist of any num- ber of time slots up to 32 If a timeslot is assigned which is beyond the number of time slots in a frame the FSX or FSR output to which it was assigned will remain inactive Two modes of operation are available Mode 1 is for sys- tems requiring different time slot assignments for the trans- mit and receive direction of each channel Mode 1 is select- ed by leaving pin 9 (MODE) open-circuit or connecting it to VCC In this case Pin 13 is the RSYNC input which defines the start of each receive frame and the four outputs FSR0–FSR3 are assigned with respect to RSYNC The XSYNC input defines the start of each transmit frame and outputs FSX0–FSX3 are assigned with respect to XSYNC XSYNC may have any phase relationship with RSYNC In- puts CH0 and CH1 select the channel from 0 to 3 (see Table Ia) Mode 2 provides the option of assigning all 8 frame sync outputs with respect to the XSYNC input Mode 2 is select- ed by connecting pin 9 (MODE) to GND This makes the TP3155 TSAC useful for either an 8-channel undirectional controller or for systems in which the transmit and receive directions of each channel are always assigned to the same time slot as the other ie the FSX and FSR inputs on the COMBO CODECFilter are hard-wired together In this case logical selection of the channel to be assigned is made via inputs CH0 CH1 and CH2 (see Table Ib) POWER-UP INITIALIZATION During power-up all frame sync outputs FSX0–FSX3 and FSR0–FSR3 are inhibited and held low No outputs will go active until a valid time slot assignment is made LOADING CONTROL DATA During the loading of control data the binary code for the selected channel must be set on inputs CH0 and CH1 (and CH2 in mode 2) see Tables Ia and Ib Control data is clocked into the DC input on the falling edges of CLKC while CS is low A new time slot assignment is transferred to the selected assignment register on the high going transition of CS The new assignment is re-synchronized to the system clock such that the new FS output pulses will start at the next complete valid time slot after the rising edge of CS TIME SLOT COUNTER OPERATION At the start of TS0 of each transmit frame defined by the first falling edge of BCLK after XSYNC goes high the trans- mit time slot counter is reset to 000000 and begins to incre- ment once every 8 cycles of BCLK Each count is compared with the 4 transmit assignment registers and on finding a match a frame sync pulse is generated at that FSX output Similarly the first falling edge of BCLK after RSYNC goes high defines the start of receive TS0 and outputs FSR0–FSR3 are generated with respect to TS0 when the receive time slot counter matches the appropriate receive assignment register TSX OUTPUT In mode 1 (separate transmit and receive assignments) this output pulls low whenever any FSX output pulse is being generated In mode 2 this output pulls low whenever any FSX or FSR output is being generated At all other times it is open-circuit allowing the TSX outputs of a number of TSACS to be wire-ANDed together with a common pull-up resistor This signal can be used to control the TRI-STATE enable input of a line driver to buffer the transmit PCM bus from the CODECFilters to the backplane TABLE Ia Control Mode 1 (TP3020TP3021 Compatible) X R T5 T4 T3 T2 T1 T0 X is the first bit clocked into the DC input Control Data Format T5 T4 T3 T2 T1 T0 Time Slot 000000 0 000001 1 000010 2 011110 30 011111 31 1 X X X X X (Note 1) CH1 CH0 Channel Selected 0 0 Assign to FSx0 andor FSR0 0 1 Assign to FSx1 andor FSR1 1 0 Assign to FSx2 andor FSR2 1 1 Assign to FSx3 andor FSR3 X R Action 0 0 Assign time slot to both selected FSX and FSR 0 1 Assign time slot to selected FSX only 1 0 Assign time slot to selected FSR only 1 1 Disable both selected FSX and FSR TABLE Ib Control Mode 2 CH2 CH1 CH0 Channel Selected 0 0 0 Assign to FSX0 0 0 1 Assign to FSX1 0 1 0 Assign to FSX2 0 1 1 Assign to FSX3 1 0 0 Assign to FSR0 1 0 1 Assign to FSR1 1 1 0 Assign to FSR2 1 1 1 Assign to FSR3 X R Action 00 0 1 Assign time slot to selected output 10 ( 1 1 Disable selected output Note 1 When T5 e 1 then the appropriate FSX or FSR output is inactive 5 |
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Description similaire - TP3155 |
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