Requirements
670
NS9750 Hardware Reference
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

Reverse
FIFO
Forward
Data
FIFO
Forward
Command
FIFO
BBUS
Slave
and
DMA
Interface
REVFWD
Host Inter f ace
BBus Interface IEEE 1284 BusIEEE 1284Peripheral PortControll er
Control
Control
Data
21
4
8
Control2
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