W83877 Winbond Electronics Corp America, W83877 Datasheet - Page 65

• Manufacturer Part Number: W83877
• Description: Winbond I/O
• Manufacturer: Winbond Electronics Corp America

5.3.13 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. The
following are required:
nStrobe (HostClk)
PD<7:0>
nAck (PeriphClk)
Busy (PeriphAck)
PError (nAckReverse)
Select (Xflag)
nAutoFd (HostAck)
nFault (nPeriphRequest)
nInit (nReverseRequest)
nSelectIn (ECPMode)
(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.
NAME
TYPE
I/O
O
O
O
O
I
I
I
I
I
The nStrobe registers data or address into the slave on the
asserting edge during write operations. This signal
handshakes with Busy.
These signals contains address or data or RLE data.
This signal indicates valid data driven by the peripheral when
asserted. This signal handshakes with nAutoFd in reverse.
This signal deasserts to indicate that the peripheral can
accept data. It indicates whether the data lines contain ECP
command information or data in the reverse direction. When
in reverse direction, normal data are transferred when Busy
(PeriphAck) is high and an 8-bit command is transferred when
it is low.
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.
Indicates printer on line.
Requests a byte of data from the peripheral when it is
asserted. This signal indicates whether the data lines contain
ECP address or data in the forward direction. When in forward
direction, normal data are transferred when nAutoFd
(HostAck) is high and an 8-bit command is transferred when it
is low.
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.
This signal sets the transfer direction (asserted = reverse,
deasserted = forward). This pin is driven low to place the
channel in the reverse direction.
This signal is always deasserted in ECP mode.
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DESCRIPTION
Publication Release Date: January 1996
W83877F
Revision A2