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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

HOST INTERFACE (HI)

Table 5-1 Host Registers after

Reset–DSP CPU Side

 

 

 

Reset Type

 

Register

Register

 

 

 

 

 

 

 

 

Name

Data

HW

SW

IR

ST

 

 

Reset

Reset

Reset

Reset

 

 

 

 

 

 

 

 

 

 

 

 

 

HF(3 - 2)

0

0

—

—

 

 

 

 

 

 

HCR

HCIE

0

0

—

—

 

 

 

 

 

HTIE

0

0

—

—

 

 

 

 

 

 

 

 

HRIE

0

0

—

—

 

 

 

 

 

 

 

DMA

0

0

0

0

 

 

 

 

 

 

 

HF(1 - 0)

0

0

0

0

 

 

 

 

 

 

HSR

HCP

0

0

0

0

 

 

 

 

 

 

 

HTDE

1

1

1

1

 

 

 

 

 

 

 

HRDF

0

0

0

0

 

 

 

 

 

 

HRX

HRX (23 - 0)

—

—

—

—

 

 

 

 

 

 

HTX

HTX (23 - 0)

—

—

—

—

 

 

 

 

 

 

5.3.2.6Host Interface DSP CPU Interrupts

The HI may request interrupt service from either the DSP or the host processor. The DSP

CPU interrupts are internal and do not require the use of an external interrupt pin (see Figure 5-11). When the appropriate mask bit in the HCR is set, an interrupt condition caused by the host processor sets the appropriate bit in the HSR, which generates an interrupt request to the DSP CPU. The DSP acknowledges interrupts caused by the host processor by jumping to the appropriate interrupt service routine. The three possible interrupts are 1) receive data register full, 2) transmit data register empty, and 3) host command. The host command can access any interrupt vector in the interrupt vector table although it has a set of vectors reserved for host command use. The DSP interrupt service routine must read or write the appropriate HI register (clearing HRDF or HTDE, for example) to clear the interrupt. In the case of host command interrupts, the interrupt acknowledge from the program controller will clear the pending interrupt condition.

5.3.2.7Host Port Usage Considerations – DSP Side

Synchronization is a common problem when two asynchronous systems are connected, and careful synchronization is required when reading multi-bit registers that are written by another asynchronous system. The considerations for proper operation on the DSP CPU side are discussed in the following paragraphs, and considerations for the host processor

5 - 18 PORT B MOTOROLA

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