DSP1620 View Datasheet(PDF) - Agere -> LSI Corporation
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DSP1620 Datasheet PDF : 114 Pages
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Preliminary Data Sheet
February 1997
DSP1628 Digital Signal Processor
4 Hardware Architecture (continued)
Finally, the assertion level of the output pins, PIBF and POBE, is controlled through bit 4, PFLAG. When PFLAG is
set low, PIBF and POBE output pins have positive assertion levels. By setting bit 5, PFLAGSEL, the logical OR of
PIBF and POBE flags (positive assertion) is seen at the output pin PIBF. By setting bit 7 in phifc, PSOBEF, the
polarity of the POBE flag in the status register, PSTAT, can be changed. PSOBEF has no effect on the POBE pin.
Pin Multiplexing
Please refer to Pin Multiplexing in Section 4.1 for a description of BIO, PHIF, VEC[3:0], and SIO2 pins.
Table 7. PHIF Function (8-bit and 16-bit Modes)
PMODE Field
0 (8-bit)
0
0
0
1 (16-bit)
1
1
1
PSTAT Pin
0
0
1
1
0
0
1
1
PBSEL Pin
0
1
0
1
0
1
0
1
PBSELF Field = 0
pdx0 low byte
reserved
PSTAT
reserved
pdx0 low byte
pdx0 high byte
PSTAT
reserved
PBSELF Field = 1
reserved
pdx0 low byte
reserved
PSTAT
pdx0 high byte
pdx0 low byte
reserved
PSTAT
Table 8. pstat Register as Seen on PB[7:0]
Bit
7
6
5
43
2
Field
RESERVED
1
PIBF
0
POBE
4.9 Bit Input/Output Unit (BIO)
The BIO controls the directions of eight bidirectional
control I/O pins, IOBIT[7:0]. If a pin is configured as an
output, it can be individually set, cleared, or toggled. If a
pin is configured as an input, it can be read and/or test-
ed.
The lower half of the sbit register (see Table 37) con-
tains current values (VALUE[7:0]) of the eight bidirec-
tional pins IOBIT[7:0]. The upper half of the sbit register
(DIREC[7:0]) controls the direction of each of the pins.
A logic 1 configures the corresponding pin as an output;
a logic 0 configures it as an input. The upper half of the
sbit register is cleared upon reset.
The cbit register (see Table 38) contains two 8-bit
fields, MODE/MASK[7:0] and DATA/PAT[7:0]. The val-
ues of DATA/PAT[7:0] are cleared upon reset. The
meaning of a bit in either field depends on whether it has
been configured as an input or an output in sbit. If a pin
has been configured to be an output, the meanings are
MODE and DATA. For an input, the meanings are
MASK and PAT(tern). Table 9 shows the functionality of
the MODE/MASK and DATA/PAT bits based on the di-
rection selected for the associated IOBIT pin.
Those bits that have been configured as inputs can be
individually tested for 1 or 0. For those inputs that are
being tested, there are four flags produced: allt (all true),
allf (all false), somet (some true), and somef (some
false). These flags can be used for conditional branch or
special instructions. The state of these flags can be
saved and restored by reading and writing bits 0 to 3 of
the alf register (see Table 39).
Table 9. BIO Operations
DIREC[n]*
1 (Output)
1 (Output)
1 (Output)
1 (Output)
0 (Input)
0 (Input)
0 (Input)
0 (Input)
MODE/
MASK[n]
0
0
1
1
0
0
1
1
DATA/
PAT[n]
0
1
0
1
0
1
0
1
Action
Clear
Set
No Change
Toggle
No Test
No Test
Test for Zero
Test for One
* 0 ≤ n ≤ 7.
If a BIO pin is switched from being configured as an out-
put to being configured as an input and then back to be-
ing configured as an output, the pin retains the previous
output value.
Pin Multiplexing
Please refer to Pin Multiplexing in Section 4.1 for a
description of BIO, PHIF, VEC[3:0], and SIO2 pins.
Lucent Technologies Inc.
25
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