Frame Phases
2-13
McBSP Operation
SPRU592E
2.4.4 Implementing the AC97 Standard With a Dual-Phase Frame
9 shows an example of the Audio Codec ‘97 (AC97) standard, which
uses the dual-phase frame feature. Notice that words, not individual bits, are
shown on the D(R/X) signal. The first phase (P1) consists of a single 16-bit
word. The second phase (P2) consists of twelve 20-bit words. The phase
configurations are listed after the figure.
Figure 2
−
9. Implementing the AC97 Standard With a Dual-Phase Frame
PxWy = Phase x Word y
D(R/X)
FS(R/X)
P2W12
P2W11
P2W10
P2W9
P2W8
P2W7
P2W6
P2W5
P2W4
P2W3
P2W2
P2W1
P1W1
ÁÁ
ÁÁ
20 bits
16 bits
1-bit data delay
-
(R/X)PHASE = 1: Dual-phase frame
-
(R/X)FRLEN1 = 0000000b: 1 word in phase 1
-
(R/X)WDLEN1 = 010b: 16 bits per word in phase 1
-
(R/X)FRLEN2 = 0001011b: 12 words in phase 2
-
(R/X)WDLEN2 = 011b: 20 bits per word in phase 2
-
CLKRP/CLKXP= 0: Receive data sampled on falling edge of internal
CLKR / transmit data clocked on rising edge of internal CLKX
-
FSRP/FSXP = 0: Active-high frame-sync signal
-
(R/X)DATDLY = 01b: Data delay of 1 clock cycle (1-bit data delay)
10 shows the timing of an AC97-standard data transfer near frame
synchronization. In this figure, individual bits are shown on D(R/X).
Specifically, the figure shows the last two bits of phase 2 of one frame and the
first four bits of phase 1 of the next frame. Regardless of the data delay, data
transfers can occur without gaps. The first bit of the second frame (P1W1B15)
immediately follows the last bit of the first frame (P2W12B0). Because a 1-bit
data delay has been chosen, the transition on the frame-sync signal can occur
when P2W12B0 is transferred.
Summary of Contents for TMS320VC5509
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Page 43: ...McBSP Operation 2 20 SPRU592E This page is intentionally left blank ...
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Page 191: ...General Purpose I O on the McBSP Pins 9 4 SPRU592E This page is intentionally left blank ...
Page 201: ...Emulation Power and Reset Considerations 10 10 SPRU592E ...
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