dsp56167 Freescale Semiconductor, Inc, dsp56167 Datasheet - Page 105

• Manufacturer Part Number: dsp56167
• Description: Advance Information 16-bit Digital Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

MOTOROLA
PORT A AND OnCE PORT DR SIGNAL LINE KEEPERS WITH RESET
External pull-up/pull-down
resistors required in all
cases.
DSP56166
Active pull-up and/or pull-down resistors have always been required for the
external bus interface pins to keep them at a valid logic state when the DSP gives up
the bus to another bus master. This is also true during hardware reset.
Adding on-chip static latches or keepers eliminates the need of including external
resistors on board when no external memory or peripherals are attached to the DSP.
When external memory and/or peripherals are desired, most if not all of the external
resistors can be eliminated. The on-chip static latch for the OnCE DR pin eliminates
the need for the eternal resistor when the OnCE is not needed.
The external bus interface control signals and the OnCE DR pins have built in reset
circuitry to guarantee that they will be initialized to the desired functional state when
the DSP comes out of hardware reset.
D0–D15
A0–A15
PEREN
PSDS
R/W
WR
RD
BG
BR
BS
BB
DF
TA
Special Design Considerations for Conversions from DSP56166 to DSP56167
Figure 4-18 DSP56167 Pull-Up/Pull-Down Resistors
33 Resistors
10 Resistors
DSP56167/D, Rev. 1
Stand-alone DSP56167
No pull-up/pull-down
resistors required.
DSP56167
D0–D15
A0–A15
PEREN
PSDS
R/W
WR
RD
BG
BR
BS
BB
DF
TA
DSP56167 with external memory/
peripheral interface.
Three pull-up resistors required.
(maximum).
*required only when used as output
enable.
DSP56167
D0–D15
A0–A15
PEREN
PSDS
R/W
WR
RD
BG
BR
BS
BB
DF
TA
Design Considerations
*
*
3 Resistors
4-29