Car Stereo System - Car Radio Digital Signal Processor User Manual
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7.1.3 Timing Parameters and Board Routing Analysis
1
2
3
4
5
6
7
8
10
11
AECLKOUT
(Output from DSP)
AECLKOUT
(Input to External Device)
Control Signals
(A)
(Output from DSP)
Control Signals
(Input to External Device)
Data Signals
(B)
(Output from External Device)
Data Signals
(B)
(Input to DSP)
9
SM320C6455-EP
FIXED-POINT DIGITAL SIGNAL PROCESSOR
SPRS462B – SEPTEMBER 2007 – REVISED JANUARY 2008
The timing parameter values specified in this data sheet do not include delays by board routings. As a
good board design practice, such delays must be taken into account. Timing values may be adjusted by
increasing/decreasing such delays. TI recommends utilizing the available I/O buffer information
specification (IBIS) models to analyze the timing characteristics correctly. To properly use IBIS models to
attain accurate timing analysis for a given system, see the Using IBIS Models for Timing Analysis
application report (literature number SPRA839 ). If needed, external logic hardware such as buffers may be
used to compensate any timing differences.
For inputs, timing is most impacted by the round-trip propagation delay from the DSP to the external
device and from the external device to the DSP. This round-trip delay tends to negatively impact the input
setup time margin, but also tends to improve the input hold time margins (see Table 7-1 and Figure 7-4 ).
Figure 7-4 represents a general transfer between the DSP and an external device. The figure also
represents board route delays and how they are perceived by the DSP and the external device.
Table 7-1. Board-Level Timing Example
(see Figure 7-4 )
NO. DESCRIPTION
1 Clock route delay
2 Minimum DSP hold time
3 Minimum DSP setup time
4 External device hold time requirement
5 External device setup time requirement
6 Control signal route delay
7 External device hold time
8 External device access time
9 DSP hold time requirement
10 DSP setup time requirement
11 Data route delay
A. Control signals include data for Writes.
B. Data signals are generated during Reads from an external device.
Figure 7-4. Board-Level Input/Output Timings
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