Texas Instruments OMAP36 Series, Technical Reference Manual

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SCM Functional Description
13.4.7.6.2 DDR Buffer Drive Strength Related Settings
The DS control maintains the same drive strength by applying programmable capacitance load
compensation at the I/O level. This is done to achieve the necessary performance of the DDR driver
output groups at different target frequencies.
Table 13-19 provides the DS programming pattern. The DS controls concern only the SDRC I/Os of the
device.
Table 13-19. DS Parameter Settings
DDR I/Os Drive Strength Setting for High-Speed I/O Cells
DS = 0b0 DS = 0b1
Equivalent load capacitance range: 2–4 pF Equivalent load capacitance range: 4–12 pF
13.4.7.6.3 High Speed I/Os Far End Load Settings
Table 13-20 provides the far-end-load range programming pattern applicable to high-speed I/Os. Control
over this signal group parameter is acquired through programming single-bit LB.
Table 13-20. LB Parameter Settings for High-Speed I/O Cells
Far End Load Setting on TL for High-Speed I/O Cells
LB = 0b0 LB = 0b1
Equivalent load capacitance: 1–10pF Equivalent load capacitance: 10–16pF
NOTE: For both capacitance load ranges, the TL length must be maintained in the range
[1cm–6cm].
13.4.7.6.4 Low-Speed I/Os Combined Slew Rate vs TL Length and Load Settings
Table 13-21 and Table 13-22 provide the recommended SC [1:0] (slew-rate control) vs LB [1:0] (combined
capacitance load and TL length control) programming pattern applicable to low-speed I/O cells. The SR
settings determine three target maximal frequencies of I/O operation.
Because the TL and SC parameter values are mutually constrained in the context of a certain I/O signal
transient performance, only the combined slew rate vs TL length/capacitance load settings make sense.
Table 13-21 and Table 13-22 list the possible SC[1:0]–LB[1:0] combinations.
Table 13-21. Recommended SC vs LB Parameter Settings for TL With Length in the Range 2–20cm
SC vs LB Settings Applicable to pads in Low-Speed I/O Cells
SC[1:0] = 00 LB[1:0] = 00 SC[1:0] = 01 LB[1:0] = 10 SC[1:0] = 10 LB[1:0] = 10
2-20 cm 2–20 cm 2–20 cm
1-10pF 10–20pF 10–20pF
achieved pad Freq <= 20MHz achieved pad Freq <= 60MHz achieved pad Freq <= 40MHz
Table 13-22. Recommended SC vs LB Parameter Settings for Dual TL With Length in the Range 20–40cm
SC vs LB Settings Applicable to Pads in Low-Speed I/O Cells
SC[1:0] = 00 LB[1:0] = 01 SC[1:0] = 01 LB[1:0] = 11 SC[1:0] = 10 LB[1:0] = 11
20-40 cm (dual TL) 20-40 cm (dual TL) 20-40 cm (dual TL)
1-10 pF 10-20 pF 10-20pF
achieved pad Freq <= 20MHz achieved pad Freq <= 60MHz achieved pad Freq <= 40MHz
2477 SWPU177N – December 2009 – Revised November 2010 System Control Module
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