MFC2000 datasheet(323/426 Pages) ETC

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Multifunctional Peripheral Controller 2000

MFC2000

100723A

Conexant

17-1

17. Bi-directional Parallel Peripheral Interface

The Parallel Peripheral Interface(PPI) controller incorporates the IEEE-1284 Compatibility/Nibble/ Byte/ ECP

protocols to offer flexible high-speed parallel data transfer. Furthermore, the PPI fully supports all variants of

these modes, including device ID requests and run-length encoded data compression. All protocols are signal-

compatible with classic parallel interfaces. The default protocol for the PPI is the Compatibility mode. The PPI

contains specific hardware to support automatic handshaking during host to peripheral,or forward, data transfers

in compatible and ECP modes, and run-length detection. The PPI also supports automatic handshaking during

peripheral to host, or reverse, data transfers in the Nibble, Byte and ECP modes. The hardware handshaking can

also be completely disabled to allow software to directly control the peripheral port interface signals and to

support new protocols as they arise in the future.

17.1 Operational Modes

The PPI supports three hardware handshaking modes for host to peripheral, or forward, data transfers. Each

mode can be enabled or disabled by software. One mode supports forward data transfers during compatibility

mode, and the other two modes support forward data transfers during ECP mode. Only one of the three modes

can be enabled at a time, or all modes can be disabled. When disabled, software must assume full responsibility

for handshaking, and use the Parallel Port Interface Register and the Parallel Port Data Register to read and

control the logic levels on all parallel port pins.

The hardware handshaking modes for peripheral to host, or reverse, data transfers are provided for Nibble, Byte

and ECP modes explained.

17.1.1 Compatibility Mode

The interface is always initialized to the compatibility Mode, a conventional, unidirectional host-to peripheral

interface. From the compatibility Mode the host may transmit data to peripheral or direct the interface to a mode

capable of transmitting data to the host. Compatibility mode hardware handshaking is enabled by setting the

MODE field to 1 in the Parallel Port Control Register. When compatibility mode is selected, the PPI interacts with

host using STROBEn, BUSY and ACKn signals.

17.1.2 P1284 Negotiation

The negotiation phase is performed under firmware control. During the negotiation, the firmware will respond to

the host stimulus by setting ACKn low, FAULTn high, SLCTOUT(XFlag) high, PE high as defined in the IEEE

1284 Specification. After the host responds to the prior signal setting, the firmware will respond with a PE low and

a FAULTn low if data to the host is available. The SLCTOUT is set to it’s appropriate value corresponding to the

extensibility feature requested by the host. (Refer to the IEEE 1284 Specification for a more complete definition of

this phase).

17.1.3 Nibble Mode

Provides an asynchronous, reverse (peripheral-to-host) channel, under control of the host. Data bytes are

transmitted as two sequential, four bit nibbles using four peripheral-to-host status lines. In Nibble

Mode(MODE=4), one byte of status data can be put to the PPI data register by CPU or DMA operation. The PPI

Logic will separate the one byte data into two nibbles and send them in sequence. The signals used in the Nibble

mode are AUTOFDn and ACKn for handshake and FAULTn, SLCTOUT, PE and BUSY for data transfer.

17.1.4 Byte Mode

Provides an asynchronous, byte-wide reverse peripheral-to-host channel using eight data lines of the interface for

data and the control/status lines for handshaking. The PPI hardware can control the handshake of the reverse

data transfer. The CPU must provide the status to send the next byte or to terminate the protocol. The MODE=5

for the Byte mode which enables a peripheral to send an entire byte of data to the PC in one data transfer cycle

using the 8 data lines, rather than the two cycles using the Nibble mode.The handshake signals are AUTOFDn,

ACKn and STROBEn.

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