Motorola DSP56012 - Manual (Page 116)

4-36 DSP56012 User’s Manual MOTOROLA
Parallel Host Interface
Host Interface (HI)
transfer request pin of a DMA controller, or a control input of external circuitry.
HOREQ is asserted when an enabled request occurs in the HI. HOREQ is deasserted
when the enabled request is cleared or masked, DMA HACK is asserted, or the DSP
is reset. HOREQ can be programmed as a GPIO pin (not open-drain) called PB13
when the HI is not being used.
4.4.6.6 Host Acknowledge (HACK)
The Port B control register allows the user to program the Host Acknowledge
(HACK) input independently of the other HI pins. When the port is configured for
GPIO, this input acts as a GPIO pin called PB14. When the port is defined as the HI,
the user can manipulate the Port B control register to configure this input as either
PB14, or as the HACK pin.
Table 4-6 shows the Port B Control register bit
configurations.
HACK can act as a data strobe for HI DMA data transfers (See Figure 4-18
on page 4-42). Or, if HACK is used as an MC68000 host interrupt acknowledge, it
enables the host Interrupt Vector Register (IVR) on the host data bus (H[7:0]) if
HOREQ is asserted (See
Figure 4-17 on page 4-41). In this case, all other HI control
pins are ignored and the state of the HI is not affected.
Note: HACK should always be pulled high when it is not in use.
Table 4-6 Port B Pin Definitions
BC0 BC1 Function
0 0 Parallel I/O (Reset Condition)
0 1 HI
1 0 HI (HACK is defined as GPIO)
1 1 Reserved