GS81314LQ19 Datasheet, PDF (14/39 Pages) GSI Technology – 144Mb SigmaQuad-IVe™ Burst of 2 Single-Bank ECCRAM™

GS81314LQ19/37GK-933/800
Signal Timing Training
Signal timing training (aka “deskew”) is often required for reliable signal transmission between components at the I/O speeds
supported by these devices. Typically, the timing training is performed in the following sequence:
Step 1: Address / Control input training.
These devices support a special Loopback Mode of operation to facilitate address / control input training.
Step 2: Read Data output training.
These devices support a special Loopback Mode of operation to facilitate read data output training.
Alternatively, slow-frequency Memory Write operations can be used to store DDR data patterns in the memory array
reliably (full-frequency Memory Write operations cannot be used because write data signals have not been trained yet),
and full-frequency Memory Read operations can then be used to train the read data output signals.
Step 3: Write Data input training.
Since address, control, and read data signals have already been trained at this point, full-frequency Memory Write and
Read operations can then be used to train the write data inputs.
Loopback Mode
These devices support two distinct Loopback Modes of operation, which can be used to:
1. Perform per-pin training on the address (SA), control (R, W), and write data clock (KD, KD) inputs.
2. Perform per-pin training on the read data (Q) outputs.
In both cases, SA, R, W, KD, KD input pin values are sampled, logically manipulated, and looped back to Q output pins.
Register bit LBKE is used to enable/disable Loopback Mode. When LBKE = 1 and MRW = 0, Loopback Mode is enabled, and
Memory Read and Write operations are blocked regardless of the states of R and W. When LBKE = 0 or MRW = 1, Loopback
Mode is disabled. See the State Truth Table for more information.
Register bits LBK[1:0] are used to select between the two distinct Loopback Modes supported by the design (controlled by LBK1),
and between the two groups of inputs used during the selected Loopback Mode (controlled by LBK0), as follows:
• LBK[1:0] = 00: selects XOR LBK Mode using Input Group 1. Loopback Mode “00”.
• LBK[1:0] = 01: selects XOR LBK Mode using Input Group 2. Loopback Mode “01”.
• LBK[1:0] = 10: selects INV LBK Mode using Input Group 1. Loopback Mode “10”.
• LBK[1:0] = 11: selects INV LBK Mode using Input Group 2. Loopback Mode “11”.
Note: For convenience, KD clocks have been included in the group of inputs that can be trained via Loopback Mode. However, 
the timing requirement for KD clocks is that their edges be tightly aligned to CK clock edges, unlike the timing requirement for
address/control signals, whose edges must be centered (approximately) between CK edges in order to optimize setup and hold
times to those CK edges. Consequently, it is questionable whether Loopback Mode can be used to train KD clocks effectively.
Loopback Latency
Loopback Latency (“LBKL”) - i.e. the number of cycles from when the inputs are sampled to when the proper result appears on the
output pins, is equal to 7 cycles.
Enabling Loopback Mode
Loopback Mode is enabled as follows:
Step 1: Initiate a Register Write operation with SA[10:1] = “000ab1.0010” to select Register #2, set LBKE = 1 to enable
Loopback Mode, and set LBK[1:0] to “ab” to select Loopback Mode “ab”.
Step 2: Wait 16 cycles for new register settings to take effect.
Loopback Mode “ab” is enabled after step 2 because MRW = 0, LBKE = 1, and LBK[1:0] = “ab”.
Rev: 1.02 3/2016
14/39
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
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