B&B Electronics Parallel Printer Card PIOC Manuale Utente Scaricare il pdf (Pagina 16)

Interfacing the Standard Parallel Port http://www.senet.com.au/~cpeacock

Interfacing the Standard Parallel Port Page 16

Bit Function

7:5 Selects Current Mode of Operation

000 Standard Mode

001 Byte Mode

010 Parallel Port FIFO Mode

011 ECP FIFO Mode

100 EPP Mode

101 Reserved

110 FIFO Test Mode

111 Configuration Mode

4 ECP Interrupt Bit

3 DMA Enable Bit

2 ECP Service Bit

1 FIFO Full

0 FIFO Empty

Table 7 ECR - Extended Control Register

The table above is of the Extended Control Register. We are only interested in the three MSB

of the Extended Control Register which selects the mode of operation. There are 7 possible modes of

operation, but not all ports will support all modes. The EPP mode is one such example, not being

available on some ports.

Modes of Operation

Standard mode Selecting this mode will cause the ECP port to behave as a Standard Parallel Port,

without bi-directional functionality.

Byte Mode / PS/2

mode

Behaves as a SPP in bi-directional mode. Bit 5 will place the port in reverse mode.

Parallel Port FIFO

mode

In this mode, any data written to the Data FIFO will be sent to the peripheral using

the SPP Handshake. The hardware will generate the handshaking required. Useful

with non-ECP devices such as printers. You can have some of the features of ECP

like FIFO buffers and hardware generation of handshaking but with the existing

SPP handshake (Centronics) instead of the ECP Handshake.

ECP FIFO mode Standard mode for ECP use. This mode uses the ECP Handshake described in

Interfacing the Extended Capabilities Port

When in ECP Mode though BIOS, and the ECR register is set to ECP FIFO Mode

(011), the SPP registers may disappear.

EPP mode/Reserved This will enable EPP Mode, if available. Under BIOS, if ECP mode is set then it’s

more than likely, this mode is not an option. However if BIOS is set to ECP and

EPP1.x Mode, then EPP 1.x will be enabled.

Under Microsoft’s Extended Capabilities Port Protocol and ISA Interface Standard this

mode is Vendor Specified.

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