MB86391 Datasheet, PDF (31/69 Pages) Fujitsu Component Limited. – MPEG2 1chip Audio/Video Encoder

(b) Read
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BCLK(O)
XBREQ(I)
XBMREQ(I)
XBGRNT(O)
XRDWR( I/O)
XAS( I/O)
ADRS27:26, 17:2(I/O)
XCS5,4(O)
XREADY( I/O)
D31:0( I/O)
XBUSEN(O)
BUSDIR(O)
All ‘ H’
All ‘ H’
RA
RA
All ‘ H’
RD
All ‘H ’
Fig. 3.1.2.1b: External resource access timing (Read)
(1) The MB86391 sets BUSDIR to 'L' (read direction) and XREADY to Hi−Z and asserts XBUSEN to
prepare for accessing.
(2) With XCSn (n = 5,4) asserted, the MB86391 selects an external resource and, in conjunction with
XAS, outputs valid data to ADRS27:26, 17:2.
(3) When the external resource outputs valid data to D31: 0 and asserts the XREADY signal in the
next cycle, the MB86391 reads the data, negates XCSn(n = 5,4), and cancels the selection.
(4) The controller sets BUSDIR to ‘H’ (write direction), negates the XBUSEN and XREADY signals,
and resets to its normal state.
Note: The external resource needs to be set to Hi−Z after setting XREADY to 'H.'
MB86391
Product Specification
Rev. 1.1
12, November 2001
27