Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
The port also supports run length encoded (RLE) decompression (required) in hardware. Compression is
accomplished by counting identical bytes and transmitting an RLE byte that indicates how many times the
next byte is to be repeated. Decompression simply intercepts the RLE byte and repeats the following byte
the specified number of times. Hardware support for compression is optional.
Table 7.3 - ECP Pin Descriptions
NAME
nStrobe
TYPE
O
DESCRIPTION
During write operations nStrobe registers data or address into the slave
on the asserting edge (handshakes with Busy).
PData 7:0
nAck
I/O
I
Contains address or data or RLE data.
Indicates valid data driven by the peripheral when asserted. This signal
handshakes with nAutoFd in reverse.
PeriphAck (Busy)
I
I
This signal deasserts to indicate that the peripheral can accept data. This
signal handshakes with nStrobe in the forward direction. In the reverse
direction this signal indicates whether the data lines contain ECP
command information or data. The peripheral uses this signal to flow
control in the forward direction. It is an “interlocked” handshake with
nStrobe. PeriphAck also provides command information in the reverse
direction.
Used to acknowledge a change in the direction the transfer (asserted =
forward). The peripheral drives this signal low to acknowledge
nReverseRequest. It is an “interlocked” handshake with
nReverseRequest. The host relies upon nAckReverse to determine when
it is permitted to drive the data bus.
PError
(nAckReverse)
Select
nAutoFd
(HostAck)
I
O
Indicates printer on line.
Requests a byte of data from the peripheral when asserted, handshaking
with nAck in the reverse direction. In the forward direction this signal
indicates whether the data lines contain ECP address or data. The host
drives this signal to flow control in the reverse direction. It is an
“interlocked” handshake with nAck. HostAck also provides command
information in the forward phase.
nFault
(nPeriphRequest)
I
Generates an error interrupt when asserted. This signal provides a
mechanism for peer-to-peer communication. This signal is valid only in
the forward direction. During ECP Mode the peripheral is permitted (but
not required) to drive this pin low to request a reverse transfer. The
request is merely a “hint” to the host; the host has ultimate control over
the transfer direction. This signal would be typically used to generate an
interrupt to the host CPU.
nInit
O
O
Sets the transfer direction (asserted = reverse, deasserted = forward).
This pin is driven low to place the channel in the reverse direction. The
peripheral is only allowed to drive the bi-directional data bus while in
ECP Mode and HostAck is low and nSelectIn is high.
nSelectIn
Always deasserted in ECP mode.
7.12 Register Definitions
The register definitions are based on the standard IBM addresses for LPT. All of the standard printer ports
are supported. The additional registers attach to an upper bit decode of the standard LPT port definition to
avoid conflict with standard ISA devices. The port is equivalent to a generic parallel port interface and may
be operated in that mode. The port registers vary depending on the mode field in the ecr. The table below
lists these dependencies. Operation of the devices in modes other than those specified is undefined.
Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)
104
SMSC LPC47M182
DATASHEET
SMSC [ SMSC CORPORATION ]
