Output Drivers
To facilitate higher performance data transfer, the use of balanced CMOS active drivers for critical signals (Data,
HostAck, HostClk, PeriphAck, PeriphClk) are used in ECP Mode. Because the use of active drivers can present
compatibility problems in Compatible Mode (the control signals, by tradition, are specified as open-collector), the
drivers are dynamically changed from open-collector to totem-pole. The timing for the dynamic driver change is
specified in then IEEE 1284 Extended Capabilities Port Protocol and ISA Interface Standard, Rev. 1.14, July 14,
1993, available from Microsoft. The dynamic driver change must be implemented properly to prevent glitching the
outputs.
t6
t3
PD<7:0>
t1
t2
t5
nSTROBE
BUSY
t4
FIGURE 22 - PARALLEL PORT FIFO TIMING
NAME
DESCRIPTION
PDATA Valid to nSTROBE Active
nSTROBE Active Pulse Width
PDATA Hold from nSTROBE Inactive (Note 1)
nSTROBE Active to BUSY Active
BUSY Inactive to nSTROBE Active
BUSY Inactive to PDATA Invalid (Note 1)
MIN
600
600
450
TYP
MAX
UNITS
ns
ns
ns
ns
t1
t2
t3
t4
t5
t6
500
680
80
ns
ns
Note 1: The data is held until BUSY goes inactive or for time t3, whichever is longer. This only applies if another data
transfer is pending. If no other data transfer is pending, the data is held indefinitely.
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