4 dax block transfer flag (xblk)—bit 3, Figure83 dax relative timing, 5 dax transmit in progress (xtip)—bit 4 – Motorola DSP56012 User Manual

Page 221: Dax block transfer flag (xblk)—bit 3 -11, Dax transmit in progress (xtip)—bit 4 -11, Figure 8-3, Dax relative timing -11

Digital Audio Transmitter

DAX Internal Architecture

MOTOROLA

DSP56012 User’s Manual

8-11

Note:

The XAUR bit is cleared by reading the XSTR register with XAUR set,
followed by writing data to XADRA and XADRB. It is also cleared by software
reset and hardware reset, and by the Stop state.

8.5.5.4

DAX Block Transfer Flag (XBLK)—Bit 3

The XBLK flag indicates that the frame being transmitted is the last frame in a block.
This bit is set at the beginning of the transmission of the last frame (the 191st frame).
This bit does not cause any interrupt. However, it causes a change in the interrupt
vector sent to DSP core in the event of an interrupt, so that a different interrupt
routine can be called (providing the next non-audio data structures for the next block
as well as storing audio data for the next frame). Writing to XADRA and XADRB
clears this bit.

Note:

Software reset, hardware reset, and the Stop state clear XBLK.

The relative timing of transmit frames and XADE and XBLK flags is shown in

Figure 8-3

on page 8-11.

8.5.5.5

DAX Transmit In Progress (XTIP)—Bit 4

The XTIP status flag indicates that the DAX is enabled and transmitting data. When
XTIP is set, it indicates that the DAX is active. When XTIP is cleared, it indicates that
the DAX is inactive. This bit provides programmers with the means to determine
whether the DAX is active or inactive. Since the DAX can be active and transmitting
data even after the XEN bit in the XCTR has been cleared (with XSTP = 1), it can be
necessary to know when the DAX actually becomes inactive. This bit is set a moment
after the DAX is enabled (XEN = 1). It is cleared either immediately (by clearing the
XEN bit, when XSTP = 0), or it is cleared at the next frame boundary (if XSTP = 1).

Note:

Software reset, hardware reset, and the Stop state clear XTIP immediately.

Figure 8-3 DAX Relative Timing

#000 #001

#008

#007

#006

#005

#004

#003

#002

#009 #010

#021

#011

#018

#017

#016

#015

#014

#013

#012

#019 #020

#022 #023

#024 #025

#032

#031

#030

#029

#028

#027

#026

#033 #034

#045

#035

#042

#041

#040

#039

#038

#037

#036

#043 #044

#046 #047

XADE

XBLK

Frame

XADE

XBLK

Frame

XADE

XBLK

Frame

#168 #169

#176

#175

#174

#173

#172

#171

#170

#177 #178

#189

#179

#186

#185

#184

#183

#182

#181

#180

#187 #188

#190 #191

AA0608