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W83627UHG
Publication Release Date: March 24, 2008
-125-
Revision 1.44
11.3.11
ECP Pin Descriptions
NAME
TYPE
DESCRIPTION
NStrobe (HostClk)
O
This pin loads data or address into the slave on its asserting edge
during write operations. This signal handshakes with Busy.
PD<7:0>
I/O
These signals contain address, data or RLE data.
nAck (PeriphClk)
I
This signal indicates valid data driven by the peripheral when
asserted. This signal handshakes with nAutoFd in reverse.
Busy (PeriphAck)
I
This signal deasserts to indicate that the peripheral can accept
data. In the reverse direction, it indicates whether the data lines
contain ECP command information or data. Normal data are
transferred when Busy (PeriphAck) is high, and an 8-bit command
is transferred when it is low.
PError (nAckReverse)
I
This signal is used to acknowledge a change in the direction of the
transfer (asserted = forward). The peripheral drives this signal low
to acknowledge nReverseRequest. The host relies upon
nAckReverse to determine when it is permitted to drive the data
bus.
Select (Xflag)
I
Indicates printer on-line.
NautoFd (HostAck)
O
Requests a byte of data from the peripheral when it is asserted. In
the forward direction, this signal indicates whether the data lines
contain ECP address or data. Normal data are transferred when
nAutoFd (HostAck) is high, and an 8-bit command is transferred
when it is low.
nFault
(nPeriphReuqest)
I
Generates an error interrupt when it is asserted. This signal is valid
only in the forward direction. The peripheral is permitted (but not
required) to drive this pin low to request a reverse transfer during
ECP mode.
nInit
(nReverseRequest)
O
This signal sets the transfer direction (asserted = reverse,
deasserted = forward). This pin is driven low to place the channel
in the reverse direction.
nSelectIn (ECPMode)
O
This signal is always deasserted in ECP mode.
11.3.12
ECP Operation
The host must negotiate on the parallel port to determine if the peripheral supports the ECP protocol
before ECP operation. After negotiation, it is necessary to initialize some of the port bits.
(a) Set direction = 0, enabling the drivers.
(b) Set strobe = 0, causing the nStrobe signal to default to the deasserted state.
(c) Set autoFd = 0, causing the nAutoFd signal to default to the deasserted state.
(d) Set mode = 011 (ECP Mode)
ECP address/RLE bytes or data bytes may be sent automatically by writing the ecpAFifo or ecpDFifo,
respectively.