dsp56366 Freescale Semiconductor, Inc, dsp56366 Datasheet - Page 11

• Manufacturer Part Number: dsp56366
• Description: Dsp56366 24-bit Audio Digital Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

Table 2-7 External Bus Control Signals (continued)
State during
Signal Name
Type
Signal Description
Reset
BG
Input
Ignored Input Bus Grant—BG is an active-low input. BG is asserted by an external bus
arbitration circuit when the DSP56366 becomes the next bus master. When BG
is asserted, the DSP56366 must wait until BB is deasserted before taking bus
mastership. When BG is deasserted, bus mastership is typically given up at the
end of the current bus cycle. This may occur in the middle of an instruction that
requires more than one external bus cycle for execution.
For proper BG operation, the asynchronous bus arbitration enable bit (ABE) in
the OMR register must be set.
BB
Input/Output
Input
Bus Busy—BB is a bidirectional active-low input/output. BB indicates that the
bus is active. Only after BB is deasserted can the pending bus master become
the bus master (and then assert the signal again). The bus master may keep
BB asserted after ceasing bus activity regardless of whether BR is asserted or
deasserted. This is called “bus parking” and allows the current bus master to
reuse the bus without rearbitration until another device requires the bus. The
deassertion of BB is done by an “active pull-up” method (i.e., BB is driven high
and then released and held high by an external pull-up resistor).
For proper BB operation, the asynchronous bus arbitration enable bit (ABE) in
the OMR register must be set.
BB requires an external pull-up resistor.
DSP56366 Technical Data, Rev. 3.1
Freescale Semiconductor
2-7