HOST INTERFACE (HI)
MOTOROLA
PORT B
5 - 33
5.3.4.3
Host Read/Write (HR/W)
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 trans-
ferred to the DSP. HR/W is stable when HEN is asserted. It can be programmed as a
general-purpose I/O pin (PB11) when the host interface is not being used, and is config-
ured as a GPIO input pin during hardware reset.
5.3.4.4
Host Enable (HEN)
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 DSP56002 data. When
HEN is asserted and HR/W is low, H0–H7 become inputs. When HEN is deasserted, host
data is latched inside the DSP. Normally, a chip select signal derived from host address
decoding and an enable clock are used to generate HEN. HEN can be programmed as a
general-purpose I/O pin (PB12) when the host interface is not being used, and is config-
ured as a GPIO input pin during hardware reset.
5.3.4.5
Host Request (HREQ)
This open-drain output signal is used by the DSP56002 HI to request service from the host
processor, DMA controller, or a simple external controller. HREQ may be connected to an
interrupt request pin of a host processor, a transfer request of a DMA controller or a con-
trol input of external circuitry. HREQ is asserted when an enabled request occurs in the
host interface. HREQ is deasserted when the enabled request is cleared or masked, DMA
HACK is asserted, or the DSP is reset. HREQ may be programmed as a general purpose
I/O pin (not open-drain) called PB13 when the HI is not being used.
5.3.4.6
Host Acknowledge (HACK)
The Port B Control register allows the user to program this input independently of the
other Host Interface pins. When the port is defined for general purpose I/O, this input acts
BC0
BC1
Function
0
0
Parallel I/O (Reset Condition)
0
1
Host Interface
1
0
Host Interface (HACK is defined as general purpose I/O)
1
1
Reserved
Table 5-6 Port B Pin Definitions
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Freescale Semiconductor, Inc.
For More Information On This Product,
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