Lucent Technologies DSP1611, Information Manual

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Information Manual DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
April 1998 Bit I/O Unit
Lucent Technologies Inc.
DRAFT COPY
10-3
10.1 BIO Hardware Function
(continued)
10.1.2 BIO Configured as Outputs (continued)
Figure 10-3 shows the BIO configured as all outputs. The bus from the DIR field of sbit controls the OUTPUT
CONTROL logic and enables the output buffers (if not enabled, the output buffers are 3-stated). The input buffers
remain connected to the sbit register and, in this case, store the value that the DSP has placed on the device pins.
If a BIO pin is switched from being an output to being an input and then back to being an output, the pin remembers
the previous output value.
5-4203
Figure 10-3. BIO Configured as Outputs
10.1.3 Pin Descriptions
IOBIT[7:0]
Each of these bits can be independently configured as either an output or an input. As outputs, they can be inde-
pendently set, toggled, or cleared under program control. As inputs, they can be tested independently or in combi-
nations for various data patterns.
Symbol Type Name/Function
IOBIT[7:0] I/O Status/Control Bits 0—7
IDB
16
OUTPUT
CONTROL
OUTPUT
BUFFERS
8
8
IOBIT[7:0]
ENABLE
DA
T
A
cbit
8 8
DATA MODE
15 8 7 0
sbit
INPUT
BUFFERS
VALUE DIR
15 8 7 0
8
8
8