at7601fg AME, Inc., at7601fg Datasheet - Page 19

• Manufacturer Part Number: at7601fg
• Description: Printer Port Controller
• Manufacturer: AME, Inc.

Rev. B.02
AT7601F
5-3-2 Operation
5-3-2.1 ECP Operation
5-3-2.2 Termination form ECP mode
Mode Switching / Software Control
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 (modes 011 or 010).
Setting the mode to 011 or 010 will cause the hardware to initiate data transfer.
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 only be changed in mode 001.
Once in an extended forward mode the software should wait for the FIFO to be empty before switching
back to mode 000 or 001. In this case all control signals will be deasserted before the mode switch. In an
ECP reverse mode the software waits for all the data to be read from the FIFO before changing back to
mode 000 or 001. Since the automatic hardware ECP reverse handshake only cares about the state of the
FIFO it may have acquired extra data which will be discarded. It may in fact be in the middle of a transfer
when the mode is changed back to 000 or 001. In this case the port will deassert AFD# independent of the
state of the transfer. The design shall not cause glitches on the handshake signals if the software meets
the constraints above.
The host may switch directions by first switching to mode=001, negotiating for the forward or reverse chan-
l Set Direction=0, enabling the drivers.
l Set Strobe=0, causing the STB# signal to default to the deasserted state.
l Set AutoFeed=0, causing the AFD# signal to default to the deasserted state.
l Set mode=011 (ECP Mode)
Note that all FIFO data transfers are byte wide and byte aligned. Address/RLE transfers are byte-wide and
ECP address/RLE bytes or data bytes may be sent automatically by writing the ECP-AFIFO or
ECP-DFIFO respectively.
only allowed in the forward direction.
for each ECP read data byte and attempt to fill the FIFO. Bytes may then be read from the ECP-DFIFO as
long as it is not empty.
ECP transfers may also be accomplished (albeit slowly) by handshaking individual bytes under program
control in mode = 001, or 000.
Termination form ECP Mode is similar to the termination from Nibble/Byte Modes. The host is permitted to
terminate from ECP Mode only is specific well-defined states. The termination can only be executed while
nel, setting direction to 1 or 0, then setting mode= 011. When direction is 1 the hardware shall handshake
After negotiation, it is necessary to initialize some of the port bits. The following are required:
the bus is in the forward direction. While the channel is in the reverse direction, it must first be transitioned
Prior to ECP operation the Host must negotiate on the parallel port to determine if the peripheral sup-
ports the ECP protocol. This is a somewhat complex negotiation carried out under program control in
mode 000.
into the forward direction.
AME, Inc.
Printer Port Controller
19