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STP2002QFP
Sun Microelectronics
Fast Ethernet, Parallel Port, SCSI (FEPS) - STP2002QFP
isters. This bit must be reset by software.
ACK_OP:
Used to specify the handshake protocol to be used on the interface. The mean-
ing of this bit differs depending on the direction of transfer. The sections on
unidirectional and bidirectional transfers should be referenced for detail in-
formation on this bit. The general definition is as follows:
1 = Handshake using PP_ACK
0 = PP_ACK is inactive
BUSY_OP:
Used to specify the handshake protocol to be used on the interface. The mean-
ing of this bit differs depending on the direction of transfer. The sections on
unidirectional and bidirectional transfers should be referenced for detail in-
formation on this bit. The general definition is as follows:
1 = Handshake performed using PP_BSY
0 = PP_BSY is not used for handshaking
EN_DIAG:
Setting this bit enables diagnostic mode which does three things:
Bits 0–2 of the output register are gated on to bits 0–2 of the input reg-
ister. This allows testing of the data path and the interrupt generation
logic.
The internal DS, ACK,andBUSY latch bits drive the internal DS_IRQ
and ACK_IRQ, and BUSY_IRQ interrupt-generation logic.
When reading the DS, ACK, and BUSY bits of the transfer control reg-
ister, the read data comes from the internal latches instead of the exter-
nal pins. During diagnostic mode, if the DS or ACK bits are configured
as outputs, the output pins will be gated to an inactive level. The BUSY
output will be driven active and the DIR output will be latched in its
current state.
ACK_DSEL:
This bit is a bidirectional select for the PP_ACK signal. When this bit is 0,
PP_ACK is an input, when 1 it is a bidirectional signal. The PP_ACKDIR pin
will reflect the direction of PP_ACK. The switching of direction is controlled
by theDIR bit of the transfer control register. The function of the two pins
is as follows:
DIR=0 DIR=1
PP_ACK Input Output