LPC47N237-MD datasheet(61/138 Pages) SMSC

61 / 138 page

3.3v I/O Controller for Port Replicators and Docking Stations

SMSC DS – LPC47N237

Page 61

Revision 0.3 (10-26-04)

DATASHEET

9.6.3

Operation

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.

ECP Operation

Prior to ECP operation the Host must negotiate on the parallel port to determine if the peripheral supports

the ECP protocol. This is a somewhat complex negotiation carried out under program control in mode 000.

After negotiation, it is necessary to initialize some of the port bits. The following are required:

Set Direction = 0, enabling the drivers.

Set strobe = 0, causing the nStrobe signal to default to the deasserted state.

Set autoFd = 0, causing the nAutoFd signal to default to the deasserted state.

Set mode = 011 (ECP Mode)

ECP address/RLE bytes or data bytes may be sent automatically by writing the ecpAFifo or ecpDFifo

respectively.

Note that all FIFO data transfers are byte wide and byte aligned. Address/RLE transfers are byte-wide and

only allowed in the forward direction.

The host may switch directions by first switching to mode = 001, negotiating for the forward or reverse

channel, setting direction to 1 or 0, then setting mode = 011. When direction is 1 the hardware shall

handshake for each ECP read data byte and attempt to fill the FIFO. Bytes may then be read from the

ecpDFifo 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 from ECP Mode

Termination from ECP Mode is similar to the termination from Nibble/Byte Modes. The host is permitted to

terminate from ECP Mode only in specific well-defined states. The termination can only be executed while

the bus is in the forward direction. To terminate while the channel is in the reverse direction, it must first be

transitioned into the forward direction.

LPC47N237-MD Datasheet(PDF) 61 Page - SMSC Corporation