MPC8280 datasheet(878/1386 Pages) FREESCALE

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Serial Management Controllers (SMCs)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

28-24

Freescale Semiconductor

Figure 28-12. Synchronization with the TSA

Once SMCMR[REN] is set, the first time-slot after the frame sync causes the SMC receiver to achieve

synchronization. Data is received immediately, but only during defined receive time slots. The receiver

continues receiving data during its defined time slots until REN is cleared. If an ENTER HUNT MODE

command is issued, the receiver loses synchronization, closes the buffer, and resynchronizes to the first

time slot after the frame sync.

Once SMCMR[TEN] is set, the SMC waits for the transmit FIFO to be loaded before trying to achieve

synchronization. When the transmit FIFO is loaded, synchronization and transmission begins depending

on the following:

•

If a buffer is made ready when the SMC2 is enabled, the first byte is placed in time slot 1 if CLSN

is 8 and to slot 2 if CLSN is 16.

•

If a buffer has its SMC enabled, then the first byte in the next buffer can appear in any time slot

associated with this channel.

•

If a buffer is ended with the L bit set, then the next buffer can appear in any time slot associated

with this channel.

If the SMC runs out of transmit buffers and a new buffer is provided later, idles are sent in the gap between

buffers. Data transmission from the later buffer begins at the start of an SMC time slot, but not necessarily

the first time slot after the frame sync. So, to maintain a certain bit alignment beginning with the first time

slot, make sure that at least one TxBD is always ready and that underruns do not occur. Otherwise, the

SMC transmitter should be disabled and reenabled. Section 28.2.4, “Disabling SMCs On-the-Fly,”

TDM Tx CLK

TDM Tx SYNC

TDM Tx

After TEN

If SMC runs out of Tx buffers and new ones

are provided later, transmission begins at

is set,

transmission

begins here.

the beginning of either time slot.

SMC1

TDM Rx CLK

TDM Rx SYNC

TDM Rx

After REN is set or after

enter hunt mode command,

reception begins here.

SMC1

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