MPC8540 datasheet(608/1302 Pages) FREESCALE

608 / 1302 page

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

13-104

Freescale Semiconductor

Local Bus Controller

All of the HDI16 peripheral’s registers are mapped directly onto the MSC8101’s QBus, as defined

by the MSC8101 16-bit Digital Signal Processor Reference Manual (order number

MSC8101RM); the transmit and receive FIFOs are mapped onto the DMA data bus such that the

DMA controller can access them directly without core intervention. The addressing for each of

these registers is defined in Section 13.5.6.1.2, “Physical Interconnections.”

The HDI16 host port itself is a 16-bit-wide parallel port with various strobe and multiplexing

options.

The most important HDI16 host port facet is that it is specified as an asynchronous interface and

so reduces concerns over clock skew between the HDI16 host port and the host device’s buses.

Furthermore, with all the host port registers being accessed with a single chip select and four

address lines, as far as the local bus is concerned, the DSP host port is akin to an asynchronous

memory mapped region. So, for the HDI16 port in single strobe mode, the host device asserts a

chip select, a single data strobe and a read/write line to select HDI16 read or write bus operations.

The read and write strobes are also used as the data latch control to complete the bus transactions,

obviating the need for any handshake termination signal from the DSP. The UPM programmer is

responsible for satisfying the AC timings of the HDI16 transactions.

Through appropriate mode selection, the HDI16 peripheral’s feature set can be fully supported by

the local bus’s UPM controlled signals. The UPM defined interface can be used with any of the

local bus’s eight chip selects to give the 16-bit port size and strobe generation that matches that of

the HDI16 host port.

Figure 13-80 shows the internal register diagram of the HDI16.

Figure 13-80. MSC8101 HDI16 Peripheral Registers

TX0

TX1

TX2

TX3

HORX

HCR

HSR

HCVR

HPCR

RX0

RX1

RX2

RX3

HOTX

ISR

ICR

CVR

QBus Data Bus

DMA Data Bus

Host Bus

MPC8540 Datasheet(PDF) 608 Page - Freescale Semiconductor, Inc

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