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STP2002QFP
Sun Microelectronics
Fast Ethernet, Parallel Port, SCSI (FEPS) - STP2002QFP
eration for transfers to and from the peripheral device.
4.3.2.1 PIO on Transfers to the Peripheral Device
For transfers to the peripheral device, all signals are under the control of soft-
ware. There is no hardware assist other than interrupt generation.
4.3.2.2 PIO on Transfers From the Peripheral Device
The two modes of bidirectional operation previously discussed are supported
with hardware-assisted data latching. The bidirectional select bits
(DS_DSEL,ACK_DSEL,BUSY_DSEL) should be set according to the de-
sired configuration. The handshake protocol bits (ACK_OP,BUSY_OP)
have no function in PIO mode.
During operation as a slave under the master write protocol (DS_DSEL=1,
DIR=1), data is sampled and latched once data strobe has been detected.
P_BSY (PP_BSY) becomes active at the same time that data is latched and
must be made inactive under software control.
During operation under master read/write protocol (DS_DSEL=0,
DIR=1), master reads are assisted by sampling and latching the data once
P_ACK (PP_ACK) has been detected.P_BSY (PP_BSY) is not generated in
this mode.