DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
Information Manual
Parallel I/O (DSP1617 Only)
April 1998
8-6
DRAFT COPY
Lucent Technologies Inc.
8.1 PIO Operation
(continued)
8.1.3 Passive Mode
In passive mode, the DSP can be used as a peripheral for other devices such as a microprocessor. Bits 12 and 11
of the pioc register configure the passive mode. If bit 12 of the pioc register is clear (0), the PODS signal becomes
an input and the contents of the DSP's parallel output register (pdx[OUT]) can be read by the external device
asserting PODS. If bit 11 of the pioc register is clear (0), PIDS is an input and the DSP's parallel input register
(pdx[IN]) can be written by the external device asserting PIDS.
Providing their respective interrupt mask bits are set (logic 1) in the pioc (or the inc register, see
for more information), the assertion of PIDS (pioc bit 7) and PODS (pioc bit 6) by an external device causes
an interrupt to the DSP to become pending. This achieves functional synchronization between the DSP and an
external device.
The function of the three PSEL pins changes whenever PIO input or output is placed in passive mode.
shows the effects of various modes on the PSEL[2:0] bits.
shows the complete encoding for PSEL[2:0] as outputs (000 corresponding to port pdx0, etc.).
If passive mode is used for either input or output, PSEL2 becomes an active-low enable or chip select. While
PSEL2 is high, the DSP ignores any activity of a passive strobe. If a DSP using passive strobes is intended to be
continuously enabled, PSEL2 should be grounded.
Whenever PODS is passive, PSEL1 becomes an input that determines whether the PIO will drive PB with the con-
tents of pdx[OUT] (i.e., the data) or the contents of PSTAT (i.e., the PIO status).
If both PIDS and PODS are passive, PSEL0 takes on a special function. It is still an output, but it is now the logical
OR of the two PIO buffer flags (PIBF and POBE). This feature is useful if the user wishes to have one signal that
will tell an external device when the DSP is ready for a PIO access. (For further explanation, see
Peripheral Mode (Host Interface)
).
Table 8-2. Function of the PSEL Pins
PODS
PIDS
PSEL2
PSEL1
PSEL0
Active
Active
Output (PSEL2)
Output (PSEL1)
Output (PSEL0)
Active
Passive
Input (enable bar)
Output (PSEL1)
Output (PSEL0)
Passive
Active
Input (enable bar)
Input (status/data)
Output (PSEL0)
Passive
Passive
Input (enable bar)
Input (status/data)
Output (PIBF | POBE)
Summary of Contents for DSP1611
Page 18: ...Chapter 1 Introduction...
Page 27: ...Chapter 2 Hardware Architecture...
Page 52: ...Chapter 3 Software Architecture...
Page 116: ...Chapter 4 Instruction Set...
Page 154: ...Chapter 5 Core Architecture...
Page 176: ...Chapter 6 External Memory Interface...
Page 208: ...Chapter 7 Serial I O...
Page 237: ...Chapter 8 Parallel I O DSP1617 Only...
Page 261: ...Chapter 9 Parallel Host Interface PHIF DSP1611 18 27 28 29 Only...
Page 275: ...Chapter 10 Bit I O Unit...
Page 284: ...Chapter 11 JTAG Test Access Port...
Page 306: ...Chapter 12 Timer...
Page 313: ...Chapter 13 Bit Manipulation Unit...
Page 325: ...Chapter 14 Error Correction Coprocessor DSP1618 28 Only...
Page 350: ...Chapter 15 Interface Guide...
Page 367: ...Appendix A Instruction Encoding...
Page 379: ...Appendix B Instruction Set Summary...
Page 381: ...aD extractz aS IM16 B 52 aD insert aS arM B 53 aD insert aS IM16 B 54 aD aS aaT B 55...
Page 437: ...Index...