SA8702

SA8702 sames 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 s s s SA8702 BLOCK MODE TIME SLOT ALLOCATION CIRCUIT PCM Switching Systems PCM Transmission Systems Subscriber Multiplex Equipment 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). Figure 1. SA8702 sames 1 02.02.93 SA8702 Operating Modes BL1 0 0 1 1 BL0 0 1 0 1 Mode of Operation Outputs Outputs Outputs Outputs active active active active in in in in timeslots 0 to 7 timeslots 8 to 15 timeslots 16 to 23 timeslots 24 to 31 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 t...