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____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
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The master then transmits two opcode bits on
SPI_MOSI. These bits specify a read, write or status
command. The value 00b represents a status command. At the same time, the slave transmits the opcode
The master then transmits 4 don’t care bits on
SPI_MOSI. During these clock periods the slave transmits 4
th bit is a status bit that indicates whether
the last access was completed successfully (1) or is still in progress (0). The 0 value indicates that the last
access has not yet completed and that another status command must follow (see section
10.3.4.3).Status=1 indicates that the last access was completed successfully. If the last access was a read then 32
bits of data follow on
SPI_MISO, starting from D31 (MSB) and ending with D0 (LSB). During these 32 clock
cycles, the master transmits 32 don’t-care bits on
SPI_MOSI. If the last access was a write the during the
next 32 clock cycles both the master and the slave must transmit don’t-care bits to complete the status
command. These 32 bits should be ignored.
Status=0 indicates that the last access was not completed and that another status command must follow.
During the next 32 clock cycles both the master and the slave must transmit don’t-care bits to complete the
status command. These 32 bits should be ignored.
The master ends the write access by deasserting
SPI_SEL_N.
The total number of
SPI_CLK cycles for a status command is 40.
Table 10-4. SPI Status Command Sequence
Bit Number
SPI_MOSI
SPI_MISO
1
Don’t care
2–3
opcode 00 (status)
Previous access opcode
4
Don’t care
5
Don’t care
6
Don’t care
7
Don’t care
8
Don’t care
Status bit: 1=access has finished, 0=access has not finished
9–40*
Don’t care*
Data*
* only if previous access was a read (previous access opcode = 10b).
10.4 Clock Structure
1
General_cfg_reg0), the clock recovery machines of the TDM-over-packet block require a 38.88MHz clock. This clock can come directly from the
CLK_HIGH pin, or the
CLAD1 block (see
Figure 6-1) can convert a 10MHz, 19.44MHz or 77.76MHz clock on
CLK_HIGH to 38.88MHz
using an analog PLL. The frequency of
CLK_HIGH must be specified in
GCR1.FREQSEL.
When common clock (differential) mode is enabled (RTP_timestamp_generation_mode=1 in
General_cfg_reg1),
the clock recovery block requires a clock on the CLK_CMN pin in addition to the clock on the
CLK_HIGH pin. See
the
CLK_CMN pin description for recommendations for the frequency of this clock. Often the same clock signal can
1
General_cfg_reg0), CPU software can disable the 38.88MHz clock output from CLAD1 to save power by setting GCR1.CLK_HIGHD. Clock recovery must be enabled whenever the TDMoP block must recover one or more service clocks from received packets using either adaptive
mode or common clock (differential) mode.