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8.1.1 Internal One-Clock Mode
In internal one-clock mode (
GCR1.CLKMODE=0) the receive direction of each TDM port uses the same clock as
the transmit direction of that port. The transmit formatter and the receive framer are therefore synchronized
together. Since the data received from the LIU receiver or the
RDATFn pin is clocked by a different clock (either the
clock recovered by the LIU or the
RCLKFn pin) the framer’s receive elastic store must be enabled so that the
difference between clock frequencies is handled by control slips in the elastic store.
Figure 8-2 is a simplified diagram of internal one-clock mode. The CLKCNTLn fields in the
FMRTOPISM registers
specify the clock to be used for each port. Choices include any of the TSYSCLKn/ECLKn input pins, any of the LIU
recovered clocks on the
RCLKn pins, any of the TDMoP recovered clocks on the
TDMn_ACLK pins, or the E1CLK
or T1CLK master clocks from the CLAD1 block. See the ref_clk[n] signal in
Figure 6-2. In addition, the SYNCNTLn
fields in the
FMRTOPISM registers specify the frame-sync pulse to be used for each port. Each port can be
configured to use any TSYNC out from any active transmit formatter. See the tsync_ref[n] signal in
Figure 6-2.
Figure 8-2. Internal One-Clock Mode
Framer port n
TCLKn
TSERn
TSYNCn
TSIGn
RSYSCLKn
RSERn
RSYNCn
RSIGn
TDMoP Block port n
TDMn_ACLK
TDMn_TCLK
TDMn_TX
TDMn_TX_SYNC
TDMn_TX_MF*
TDMn_TSIG
TDMn_RCLK
TDMn_RX
TDMn_RX_SYNC
TDMn_RSIG
TCLKOn
TPOSn
TNEGn
RCLKn
RPOSn
RNEGn
ACLKn
RCLKn
Connected to LIU
TSYNC
TSYNC[8..1]
*Note: The internal signal input "TDMn_TX_MF" is a don't care when configured in framed mode.
SYNCNTL
bits
ECLK[8..1] pin
ACLK[8..1]
RCLK[8..1]
CLKCNTL
bits
E1CLK
T1CLK
8.1.2 Internal Two-Clock Mode
In internal two-clock mode
(GCR1.CLKMODE=1) the receive direction and the transmit direction of each TDM port
have separate clocks. In this mode data is clocked all the way through the receive framer by the LIU’s recovered
clock or the
RCLKFn signal and therefore the framer’s receive elastic store does not need to be enabled.
Figure 8-3 is a simplified diagram of internal two-clock mode for framed and multiframed applications. The
CLKCNTLn fields in the
FMRTOPISM registers specify the clock to be used for the transmit side of each port.
Choices include any of the TSYSCLKn/ECLKn input pins, any of the LIU recovered clocks on the
RCLKn pins, any
of the TDMoP recovered clocks on the
TDMn_ACLK pins, or the E1CLK or T1CLK master clocks from the CLAD1
block. See the ref_clk[n] signal in
Figure 6-2. In addition, the SYNCNTLn fields in the
FMRTOPISM registers
specify the frame-sync pulse to used for the transmit side of each port. Each port can be configured to use any
TSYNC out from any active transmit formatter. See the tsync_ref[n] signal in
Figure 6-2. On the receive side, the
clock is typically the RCLKn signal for the port as shown in
Figure 8-3 while the frame sync signal is the
RF/MSYNCn signal.
If framing is not needed for a particular application, the device can be configured for unframed mode by setting
GCR1.UNFRMMODE=1. In this mode receive frame sync and signaling are squelched between the framer and the