Motorola DSP56012 User Manual page 51

Signal Name Type
HR/W Input
PB11 Input/
Output
HEN Input
PB12 Input/
Output
HOREQ Open-
drain
Output
PB13 Input/
Output
MOTOROLA
Table 2-6 Host Interface (Continued)
State During
Reset
Input Host Read/Write—This input selects the direction of
data transfer for each host processor access. If HR/W is
high and HEN is asserted, H0–H7 are outputs and DSP
data is transferred to the host processor. If HR/W is low
and HEN is asserted, H0–H7 are inputs and host data is
transferred to the DSP. HR/W must be stable when
HEN is asserted.
Port B GPIO 11 (PB11)—This signal is a General
Purpose I/O signal (PB11) when the Host Interface is
not being used.
After reset, the default state for this signal is GPIO
input.
Input Host Enable—This input enables a data transfer on the
host data bus. When HEN is asserted and HR/W is
high, H0–H7 become outputs and the host processor
may read DSP56011 data. When HEN is asserted and
HR/W is low, H0–H7 become inputs. Host data is
latched inside the DSP on the rising edge of HEN.
Normally, a chip select signal derived from host address
decoding and an enable strobe are used to generate
HEN.
Port B GPIO 12 (PB12)—This signal is a General
Purpose I/O signal (PB12) when the Host Interface is
not being used.
After reset, the default state for this signal is GPIO
input.
Input Host Request— This signal is used by the Host Interface
to request service from the host processor, DMA
controller, or a simple external controller.
Note:
Port B GPIO 13 (PB13)—This signal is a General
Purpose (not open-drain) I/O signal (PB13) when the
Host Interface is not selected.
After reset, the default state for this signal is GPIO
input.
DSP56012 User's Manual
Signal Description
HOREQ should always be pulled high when it
is not in use.
Signal Descriptions
Host Interface (HI)
2-11