Motorola DSP56012 - Manual (Page 51)

Signal Descriptions
Host Interface (HI)
MOTOROLA DSP56012 User’s Manual 2-11
HR/W
PB11
Input
Input/
Output
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.
HEN
PB12
Input
Input/
Output
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.
HOREQ
PB13
Open-
drain
Output
Input/
Output
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: HOREQ should always be pulled high when it
is not in use.
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.
Table 2-6 Host Interface (Continued)
Signal Name Type
State During
Reset
Signal Description