DSP1611/17/18/27/28/29 DIGITAL SIGNAL PROCESSOR
Information Manual
Serial I/O
April 1998
7-6
DRAFT COPY
Lucent Technologies Inc.
7.1 SIO Operation
(continued)
7.1.3 Output Section
If the DSP device is reset (powerup or RSTB), the output buffer empty (OBE) status flag and signal are set indicat-
ing the buffer is empty. If data is written to the output buffer by an instruction of the form sdx = a0, sdx = a1,
sdx = Y, or sdx = VALUE, OBE is cleared and the serial output section is ready for a serial transmission. The sta-
tus of the OBE flag can be read from either bit 3 of the pioc
1
register or bit 1 of the ins register (OBE interrupt sta-
tus bit). The OBE flag can be used as an interrupting condition by setting the OBE interrupt enable bit in either the
inc register (bit 1) or the pioc
1
register (bit 8) for vectored interrupts.
shows the timing relationships for the SIO output port signals in passive mode (passive mode is defined
here as OLD being supplied by an external device). A typically free-running clock (OCK) synchronizes all events
taking place within the output section. A high-to-low transition of the output load (OLD) signal followed by the next
rising edge of OCK initiates the start of an output transaction. This procedure causes the contents of the output
buffer register (sdx[out]) to be transferred to the output shift (OSR) register, the OBE flag and signal to be set (indi-
cating the need for more data), and the first serial data bit to be placed on the data output (DO) pin. One option
available on the DSP1627/28/29 is to have the data placed on the DO pin on the falling edge of OCK rather than
the rising edge. This is accomplished by setting bit 10 (DODLY) of the sioc (sioc2) register.
Each data bit is then output on successive rising edges of OCK. Eight or 16 bits later (depending on the word size
selected by the sioc OLEN field) when the serial output has been completed, an internal signal indicates that the
last bit of the serial transmission has been sent. If the output buffer has been reloaded, another transfer begins
immediately; otherwise, zeros are sent on the serial output until the buffer is reloaded prior to a high-to-low transi-
tion of OLD to begin another transmission. Double-buffering allows the output buffer to be reloaded while data is
being shifted out of the output shift register.
The OBE flag and signal are negated if the output buffer is reloaded via a write to the sdx register synchronized
with a falling edge of CKO.
5-4176
Figure 7-6. SIO Passive Mode Output Timing, 16-bit Words
1.DSP1617 only.
CKO
sdx = a0
OLD
OCK
DO
SADD
OBE
DOEN
B0
B2 B3
B15 B0
B1
B1
AD0
AD7 AS0
AS7 AD0
AD7
sdx = a0
Содержание DSP1611
Страница 18: ...Chapter 1 Introduction...
Страница 27: ...Chapter 2 Hardware Architecture...
Страница 52: ...Chapter 3 Software Architecture...
Страница 116: ...Chapter 4 Instruction Set...
Страница 154: ...Chapter 5 Core Architecture...
Страница 176: ...Chapter 6 External Memory Interface...
Страница 208: ...Chapter 7 Serial I O...
Страница 237: ...Chapter 8 Parallel I O DSP1617 Only...
Страница 261: ...Chapter 9 Parallel Host Interface PHIF DSP1611 18 27 28 29 Only...
Страница 275: ...Chapter 10 Bit I O Unit...
Страница 284: ...Chapter 11 JTAG Test Access Port...
Страница 306: ...Chapter 12 Timer...
Страница 313: ...Chapter 13 Bit Manipulation Unit...
Страница 325: ...Chapter 14 Error Correction Coprocessor DSP1618 28 Only...
Страница 350: ...Chapter 15 Interface Guide...
Страница 367: ...Appendix A Instruction Encoding...
Страница 379: ...Appendix B Instruction Set Summary...
Страница 381: ...aD extractz aS IM16 B 52 aD insert aS arM B 53 aD insert aS IM16 B 54 aD aS aaT B 55...
Страница 437: ...Index...