Requirements, Overview, Pin under software control – Digi NS9750 User Manual
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Requirements
Two components are required to run the IEEE 1284 peripheral-to-host interface:
Clock divider. Required to generate the 1284-port operating clock from the
BBus clock. The operating range of the port clock typically is 100 KHz–2
MHz. The clock divider is set using the granularity counter (see "Granularity
Count register" on page 702).
External transceivers. The data flow direction control is provided using a
GPIO
pin under software control.
Overview
Figure 95 shows the block diagram of the IEEE 1284 peripheral port control module.
Figure 95: IEEE 1284 peripheral port control module
Rev erse
FIFO
Forward
Data
FIFO
Forward
Command
FIFO
BBUS
Slave
and
DMA
Interface
R
E
V
F
W
D
H
o
s
t
In
te
rf
a
c
e
BBus Interface
IEEE 1284 Bus
IEEE 1284
Peripheral Port
Controller
Control
Control
Data
21
4
8
Control
2
Data
8
Control
Data
8
2
Control
4
Data
8
Control
2
Data
8
Control
2
Data
8
Control
2
Data
8
Data
8
Control
4