DS33R41 Maxim Integrated Products, DS33R41 Datasheet - Page 113

• Manufacturer Part Number: DS33R41
• Description: Network Controller & Processor ICs Inverse-Multiplexing Ethernet Mapper wit
• Manufacturer: Maxim Integrated Products

DS33R41 Inverse-Multiplexing Ethernet Mapper with Quad Integrated T1/E1/J1 Transceivers
11.2 Programmable Backplane Clock Synthesizer
The transceiver contains an on-chip clock synthesizer that generates a user-selectable clock output on the BPCLK
pin, referenced to the recovered receive clock (RCLKn). The synthesizer uses a phase-locked loop to generate
low-jitter clocks. Common applications include generation of port and backplane system clocks. The TR.CCR2
register is used to enable (TR.CCR2.0) and select (TR.CCR2.1 and TR.CCR2.2) the clock frequency of the BPCLK
pin.
11.3 Fractional T1/E1 Support
Fractional T1/E1 communication is supported on T1/E1 transceivers not being actively used for the transfer of
packet data. The user should take care to fill all unused timeslots on the RSERI pin with all 1s.
The T1/E1/J1 transceiver can be programmed to output gapped clocks for selected channels in the receive and
transmit paths to simplify connections into a USART or LAPD controller in fractional T1/E1 or ISDN-PRI
applications. The receive and transmit paths have independent enables. Channel formats supported include
56kbps and 64kbps. This is accomplished by assigning an alternate function to the RCHCLK and TCHCLK pins.
Setting TR.CCR3.0 = 1 causes the RCHCLK pin to output a gapped clock as defined by the receive fractional
T1/E1 function of the TR.PCPR register. Setting TR.CCR3.2 = 1 causes the TCHCLK pin to output a gapped clock
as defined by the transmit fractional T1/E1 function of the TR.PCPR register. TR.CCR3.1 and TR.CCR3.3 can be
used to select between 64kbps and 56kbps operation. See Section
10.2
for details about programming the per-
channel function. In T1 mode no clock is generated at the F-bit position.
When 56kbps mode is selected, the LSB clock in the channel is omitted. Only the seven most significant bits of the
channel have clocks.
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