W83787IF Datasheet, PDF (57/123 Pages) Winbond – WINBOND I/O WITH SERIAL-INFRARED SUPPORT

W83787IF
ECP Pin descriptions, continued
NAME
nFault (nPeriphRequest)
nInit (nReverseRequest)
nSelectIn (ECPMode)
TYPE
DESCRIPTION
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.
O This signal sets the transfer direction (asserted = reverse,
deasserted = forward). This pin is driven low to place the
channel in the reverse direction.
O This signal is always deasserted in ECP mode.
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:
(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.
Mode Switching
Software will execute P1284 negotiation and all operation prior to a data transfer phase under
programmed I/O control (mode 000 or 001). Hardware provides an automatic control line handshake,
moving data between the FIFO and the ECP port only in the data transfer phase (mode 011 or 010).
If the port is in mode 000 or 001 it may switch to any other mode. If the port is not in mode 000 or 001
it can only be switched into mode 000 or 001. The direction can be changed only in mode 001.
When in extended forward mode, the software should wait for the FIFO to be empty before switching
back to mode 000 or 001. In ECP reverse mode the software waits for all the data to be read from the
FIFO before changing back to mode 000 or 001.
Command/Data
ECP mode allows the transfer of normal 8-bit data or 8-bit commands. In the forward direction,
normal data are transferred when HostAck is high and an 8-bit command is transferred when HostAck
is low. The most significant bits of the command indicate whether it is a run-length count (for
compression) or a channel address.
In the reverse direction, normal data are transferred when PeriphAck is high and an 8-bit command is
transferred when PeriphAck is low. The most significant bit of the command is always zero.
Data Compression
The W83787IF supports run length encoded (RLE) decompression in hardware and can transfer
compressed data to a peripheral. Note that the odd (RLE) compression in hardware is not supported.
In order to transfer data in ECP mode, the compression count is written to the ecpAFifo and the data
byte is written to the ecpDFifo.
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Publication ReleaseDate:Sep 1995
Revision A1