1.6.1.7.3. TX Path
- Tail bits padding block—pads incoming data (jesd204_tx_datain) with "0" if N < 16, so that the padded data is 16 bits per sample.
- Assembling block—arranges the resulting data bits in a specific way according to the mapping scheme (refer to figure).
- Multiplexing block—sends the multiplexed data to the DLL interface, determined by certain control signals from the TX control block.
Parameter | Description | Value |
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L | Number of lanes per converter device. | 1–8 |
F | Number of octets per frame. | 1, 2, 4, 8 |
CS | Number of control bits per conversion sample. | 0–3 |
N | Number of conversion bits per converter. | 12-16 |
N' | Number of transmitted bits per sample in the user data format. | 16 |
F1_FRAMECLK_DIV | Only applies to cases where F=1. The divider ratio on the frame_clk. The assembler always use the post-divided frame_clk (txframe_clk). 6 |
1, 4 |
F2_FRAMECLK_DIV | Only applies to cases where F=2. The divider ratio on the frame_clk. The assembler always use the post-divided frame_clk (txframe_clk). 6 |
1, 2 |
RECONFIG_EN | Enable reconfiguration support in the transport layer. Only downscaling reconfiguration is supported. Disable the reconfiguration to reduce the logic. | 0, 1 |
DATA_BUS_WIDTH | The data input bus width size that depends on the F and L. bus_width = M*S*N F = (M*S*N_PRIME)/(8*L) M*S = (8*F*L)/N_PRIME Therefore the data bus width = (8*F*L*N)/N_PRIME |
(8*F*L*N)/N_PRIME |
CONTROL_BUS_WIDTH | The control input bus width size. The width depends on the CS parameter as well as the M and S parameters. When CS is 0, the control data is one bit wide (tie the signal to 0). If CS = 0, the bus width = 1. Otherwise, the bus width = (DATA_BUS_WIDTH/N*CS) while DATA_BUS_WIDTH/N = M*S |
OUTPUT_BUS_WIDTH/N*CS |
Signal |
Clock Domain |
Direction |
Description |
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Control Unit | |||||||||||||
txlink_clk | — |
Input |
TX link clock signal. This clock is equal to the TX data rate divided by 40. This clock is synchronous to the txframe_clk signal. | ||||||||||
txframe_clk | — |
Input |
TX frame clock used by the transport layer. The frequency is a function of parameters F, F1_FRAMECLK_DIV, F2_FRAMECLK_DIV and txlink_clk. This clock is synchronous to the txlink_clk signal. |
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txlink_rst_n | txlink_clk | Input |
Reset for the TX link clock domain logic in the assembler. This reset is an active low signal and the deassertion is synchronous to the rising-edge of txlink_clk. | ||||||||||
txframe_rst_n | txframe_clk | Input |
Reset for the TX frame clock domain logic in the assembler. This reset is an active low signal and the deassertion is synchronous to the rising-edge of txframe_clk. | ||||||||||
Signal |
Clock Domain |
Direction |
Description |
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Between Avalon- ST and Transport Layer | |||||||||||||
jesd204_tx_ datain[(DATA_BUS_WIDTH)-1:0] | txframe_clk | Input |
TX data from the Avalon-ST source interface. The source shall arrange the data in a specific order, as illustrated in the cases listed in TX Path Data Remapping section | ||||||||||
jesd204_tx_controlin[(CONTROL_BUS_WIDTH)-1:0] | txframe_clk | Input | TX control data from the Avalon-ST source interface. The source shall arrange the data in a specific order, as illustrated in the cases listed in TX Path Data Remapping section | ||||||||||
jesd204_tx_data_valid | txframe_clk | Input |
Indicates whether the data from the Avalon-ST source interface to the transport layer is valid or invalid.
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jesd204_tx_data_ready | txframe_clk |
Output |
Indicates that the transport layer is ready to accept data from the Avalon-ST source interface.
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Signal |
Clock Domain |
Direction |
Description |
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Between Transport Layer and DLL | |||||||||||||
jesd204_tx_link_datain[(L*32)-1:0] | txlink_clk |
Output |
Indicates transmitted data from the transport layer to the DLL at txlink_clk clock rate, where four octets are packed into a 32-bit data width per lane. The data format is big endian. The table below illustrates the data mapping for L = 4:
Connect this signal to the TX DLL jesd204_tx_link_data[] input pin. |
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jesd204_tx_link_data_valid | txlink_clk |
Output |
Indicates whether the jesd204_tx_link_datain[] is valid or invalid.
Connect this signal to the TX DLL jesd204_tx_link_valid input pin. |
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jesd204_tx_link_early_ready 7 | txlink_clk | Input |
Indicates that the DLL requires valid data at the subsequent implementation-specific duration. Connect this signal to the TX DLL jesd204_tx_frame_ready output pin. |
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jesd204_tx_link_error | txlink_clk |
Output |
Indicates an error at the Avalon-ST source interface. Specifically, this signal is asserted when jesd204_tx_data_valid = "0" while jesd204_tx_data_ready = "1". The DLL subsequently reports this error to the CSR block. Connect this signal to the TX DLL jesd204_tx_frame_error input pin. |
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Signal |
Clock Domain |
Direction |
Description |
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CSR in DLL | |||||||||||||
csr_l[4:0] 8 | mgmt_clk | Input |
Indicates the number of active lanes for the link. This 5-bit bus represents the L value in zero-based binary format. For example, if L = 1, the csr_l[4:0] = "00000". This design example supports the following values:
Runtime reconfiguration supports L fallback. For static configuration, set the maximum L and reconfigure csr_l[] to a smaller value during runtime. This transport layer only supports higher index channels to be powered down. To interleave the de-commision channels, you need to modify the interface connection from the DLL to transport layer. Connect this signal to the TX DLL csr_l[] output pin. |
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csr_f[7:0] 8 | mgmt_clk | Input |
Indicates the number of octets per frame. This 8-bit bus represents the F value in zero-based binary format. For example, if F = 2, the csr_f[7:0] = "00000001". This design example supports the following values:
Any programmed value beyond the supported range may result in undeterminable behavior in the transport layer. Ensure that the csr_f[7:0] value always matches the system parameter F value when it is in static configuration. Connect this signal to the TX DLL csr_f[] output pin. |
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csr_n[4:0] 8 | mgmt_clk | Input |
Indicates the converter resolution. This 5-bit bus represents the N value in zero-based binary format. For example, if N = 16, the csr_n[4:0] = "01111". This design example supports the following values:
Connect this signal to the TX DLL csr_n[] output pin. |
TX Path Operation
Operation:
- Upon the deassertion of the txframe_rst_n signal, the jesd204_tx_link_early_ready signal from the DLL to the transport layer is asserted some time later, which activates the transport layer to start sampling the jesd204_tx_datain[15:0] signal from the Avalon-ST interface.
- Each sampled 16-bit data is first written in a FIFO with a depth of four.
- Once the FIFO accumulates 32-bit data, the data is streamed to the DLL accordingly through the jesd204_tx_link_datain[31:0] signal.
- Finally, the jesd204_tx_link_early_ready and jesd204_tx_data_ready signals deassert because the DLL has entered code group synchronization state in this scenario.
TX Data Transmission
Upon the deassertion of txframe_rst_n signal, the link's jesd204_tx_link_early_ready signal equals to "1". This setting activates the TL to start sampling jesd204_tx_datain signal from the Avalon-ST interface and transmits sampled data (jesd204_tx_link_datain) to the TX link. The TX link only captures valid data from the TL when the jesd204_tx_link_ready signal equals to "1" (in user data phase). This means all the data transmitted from the TL before jesd204_tx_link_ready signal equals to "1" are ignored.
TX Path Data Remapping
- The application layer or user logic data path interfaces directly with the transport layer through the Avalon-ST data bus if the application layer operates in frame clock domain. If the application layer operates at a different clock domain than the frame clock domain, add a FIFO for the clock domain crossing.
- You have to reorder the samples so that sample 0 of converter 0 is located at LSB of the Avalon-ST data bus, followed by sample 1 of converter 0 (if S>1) or sample 0 of converter 1 (if S=1). The most significant bits (MSB) of the Avalon-ST bus has a sample of S -1 of converter M-1. For example, if S=4 and M=4, the most significant bits will be occupied by sample 3 of converter 3.
- In this example, there is no control word because CF=0. Control bits are added if CS>1. Depending on the value of CS and N, the number of tail bits added is N'-N-CS. For example, N'=16, N=12 and CS=2, the number of tail bits added to form a nibble group (NG) is 2.
- The JESD204B IP core implements the data transfer in big endian format. Data is reshuffled in big endian format before crossing to the link clock domain through an adaptor.
- The data is arranged so that the L0 is always on the right (LSB) in the data bus interfacing with the JESD204B IP core. In big endian implementation, the oldest data (F0) is placed at the MSB in L0. 32-bits or 4 octets of data are transferred to the IP core in one link clock cycle. For example of F=8, 2 link clock cycles are needed to transfer all 8 octets to the IP core.
The following tables show examples of data mapping for L=4, F=1, 2, 4, 8 and M*S=2, 4, 8, 16. The configurations that the transport layer support are not limited to these examples.
F = 1 | ||||
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Supported M and S | M*S=2 for F=1, L=4 F=1 supports either (case1: M=1, S=2) or (case2: M=2, S=1) |
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F1_FRAMCLK_DIV=19 | 1st frameclk | jesd204_tx_datain[31:0] = {F8F12, F0F4} | Case1: M=1, S=2 | M0S0=F0F4, M0S1=F8F12 |
Case2: M=2, S=1 | M0S0=F0F4, M1S0=F8F12 | |||
2nd frameclk | jesd204_tx_datain[31:0] = {F9F13, F1F5} | Case1: M=1, S=2 | M0S0=F1F5, M0S1=F9F13 | |
Case2: M=2, S=1 | M0S0=F1F5, M1S0=F9F13 | |||
3rd frameclk | jesd204_tx_datain[31:0] = {F10F114, F2F6} | Case1: M=1, S=2 | M0S0=F2F6, M0S1=F10F14 | |
Case2: M=2, S=1 | M0S0=F2F6, M1S0=F10F14 | |||
4th frameclk | jesd204_tx_datain[31:0] = {F11F15, F3F7} | Case1: M=1, S=2 | M0S0=F3F7, M0S1=F11F15 | |
Case2: M=2, S=1 | M0S0=F3F7, M1S0=F11F15 | |||
F1_FRAMCLK_DIV=4 10 | jesd204_tx_datain[127:0] = {{F11F15, F3F7},{F10F114, F2F6},{F9F13, F1F5},{F8F12, F0F4}} | |||
Lane | L3 | L2 | L1 | L0 |
Data Out | {F12, F13, F14, F15} | {F8, F9, F10, F11} | {F4, F5, F6, F7} | {F0, F1, F2, F3} |
F = 2 | ||||
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Supported M and S | M*S=4 for F=2, L=4 F=2 supports either (case1: M=1, S=4), (case2: M=2, S=2) or (case3: M=4, S=1) |
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F2_FRAMCLK_DIV=1 | 1st frameclk | jesd204_tx_datain[63:0] = {F12F13, F8F9,F4F5, F0F1} |
Case1: M=1, S=4 | M0S0=F0F1, M0S1=F4F5, M0S2=F8F9, M0S3=F12F13 at |
Case2: M=2, S=2 | M0S0=F0F1, M0S1=F4F5, M1S0=F8F9, M1S1=F12F13 | |||
Case3: M=4, S=1 | M0S0=F0F1, M1S0=F4F5, M2S0=F8F9, M3S0=F12F13 | |||
2nd frameclk | jesd204_tx_datain[63:0] = {F14F15, F10F11,F6F7, F2F3} |
Case1: M=1, S=4 | M0S0=F2F3, M0S1=F6F7, M0S2=F10F11, M0S3=F14F15 | |
Case2: M=2, S=2 | M0S0=F2F3, M0S1=F6F7, M1S0=F10F11, M1S1=F14F15 | |||
Case3: M=4, S=1 | M0S0=F2F3, M1S0=F6F7, M2S0=F10F11, M3S0=F14F15 | |||
F2_FRAMCLK_DIV=2 | jesd204_tx_datain[127:0] = {{F14F15, F10F11,F6F7, F2F3}, {F12F13, F8F9,F4F5, F0F1}} |
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Lane | L3 | L2 | L1 | L0 |
Data Out | {F12, F13, F14, F15} | {F8, F9, F10, F11} | {F4, F5, F6, F7} | {F0, F1, F2, F3} |
F = 4 | ||||
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Supported M and S | M*S=8 for F=4, L=4 F=4 supports either (case1: M=1, S=8), (case2: M=2, S=4), (case3: M=4, S=2) or (case4: M=8, S=1) |
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F=4 | jesd204_tx_datain[127:0] = {F14F15,F12F13, F10F11, F8F9,F6F7,F4F5, F2F3,F0F1} |
Case1: M=1, S=8 | {M0S7, M0S6, M0S5, M0S4, M0S3, M0S2, M0S1, M0S0} | |
Case2: M=2, S=4 | {M1S3, M1S2, M1S1, M1S0, M0S3, M0S2, M0S1, M0S0} | |||
Case3: M=4, S=2 | {M3S1, M3S0, M2S1, M2S0, M1S1, M1S0, M0S1, M0S0} | |||
Case4: M=8, S=1 | {M7S0, M6S0, M5S0, M4S0, M3S0, M2S0, M1S0, M0S0} | |||
Lane | L3 | L2 | L1 | L0 |
Data Out | {F12, F13, F14, F15} | {F8, F9, F10, F11} | {F4, F5, F6, F7} | {F0, F1, F2, F3} |
F = 8 | ||||
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Supported M and S | M*S=16 for F=8, L=4 F=8 supports either (case1: M=1, S=16), (case2: M=2, S=8), (case3: M=4, S=4), (case4: M=8, S=2) or (case5: M=16, S=1) |
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F=8 | jesd204_tx_datain[255:0] = {{F3031, F28F29,F26F27, F24F25}, {F22F23, F20F21,F18F19, F16F17}, {F14F15, F12F13,F10F11, F8F9}, {F6F7,F4F5, F2F3,F0F1}} |
Case1: M=1, S=16 | {M0S15, M0S14, M0S13, M0S12, M0S11, M0S10, M0S9, M0S8, M0S7, M0S6, M0S5, M0S4, M0S3, M0S2, M0S1, M0S0} | |
Lane | L3 | L2 | L1 | L0 |
Data Out at linkclk T0 | {F24, F25, F26, F27} | {F16, F17, F18, F19} | {F8, F9, F10, F11} | {F0, F1, F2, F3} |
Data Out at linkclk T1 | {F28, F29, F30, F31} | {F20, F21, F22, F23} | {F12, F13, F14, F15} | {F4, F5, F6, F7} |
TX Error Reporting
For TX path error reporting, the transport layer expects a valid stream of TX data from the Avalon-ST interface (indicated by jesd204_tx_data_valid signal = 1) as long as the jesd204_tx_data_ready remains asserted. If the jesd204_tx_data_valid signal unexpectedly deasserts during this stage, the transport layer reports an error to the DLL by asserting the jesd204_tx_link_error signal and deasserting the jesd204_tx_link_data_valid signal accordingly, as shown in the timing diagram below.
TX Latency
F | FRAMECLK_DIV | TX Latency |
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1 | 1 | 3 txframe_clk period.
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1 | 4 | 1 txframe_clk period |
2 | 1 | 3 txframe_clk period.
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2 | 2 | 1 txframe_clk period |
4 | — | 1 txframe_clk period |
8 | — | 1 txframe_clk period |