
Data Sheet
June 2001
DSP16410B Digital Signal Processor
142
Agere Systems—Proprietary
Use pursuant to Company instructions
Agere Systems Inc.
4 Hardware Architecture
(continued)
4.15 Parallel Interface Unit (PIU)
(continued)
4.15.4 Host Register Read and Write Cycles
This section describes typical host read and write
cycles of PIU registers for both Inteland Motorola
hosts.
Figure 39 on page 143
is a functional timing dia-
gram of a register read and a register write cycle for
both an Inteland a Motorolahost. The address that
the host applies to PADD[3:0] during the cycle deter-
mines how the host accesses the register, i.e., deter-
mines the host command. See
Section 4.15.5 on page
144
for details on host commands.
The following sequence corresponds to the Intel host
read of the
PAH
,
PAL
,
PCON
, or
DSCRATCH
register
shown in
Figure 39
:
1. The host drives a valid address onto PADD[3:0].
The host must hold PIDS high for the entire duration
of the access.
2. The host initiates the cycle by asserting (low) PCSN
and PODS.
3. The PIU drives the contents of the register onto
PD[15:0].
4. The host concludes the cycle by deasserting PCSN
or PODS and latching the data from PD[15:0].
5. The PIU 3-states PD[15:0].
The following sequence corresponds to the Intel host
write of the
PAH
,
PAL
,
PCON
, or
HSCRATCH
register
shown in
Figure 39
. The PIU uses the
PDI
register to
temporarily hold the write data.
1. The host drives a valid address onto PADD[3:0].
The host must hold PODS high for the entire dura-
tion of the access.
2. The host initiates the cycle by asserting (low) PCSN,
PIDS, and PRWN.
3. The host drives data onto PD[15:0].
4. If
PDI
is empty, the PIU notifies the host by asserting
PRDY and deasserting PIBF. If
PDI
is still full from a
previous host write, the host must wait until the PIU
asserts PRDY.
5. The host concludes the cycle by deasserting PCSN
or PIDS, causing the PIU to latch the data from
PD[15:0] into
PDI
. The PIU transfers the data in
PDI
into
PAH
,
PAL
,
PCON
, or
HSCRATCH
.
6. The host 3-states PD[15:0].
The following sequence corresponds to the Motorola
read of the
PAH
,
PAL
,
PCON
, or
DSCRATCH
register
shown in
Figure 39
. In the figure and in the timing
sequences described below, it is assumed that PIDS is
tied high, selecting an active-low data strobe (PODS).
1. The host drives a valid address onto PADD[3:0].
The host must hold PRWN high for the duration of
the access.
2. The host initiates the cycle by asserting (low) PCSN
and PODS
3. The PIU drives the data in the register onto
PD[15:0].
4. The host concludes the cycle by deasserting PCSN
or PODS and latching the data from PD[15:0].
5. The PIU 3-states PD[15:0].
The following sequence corresponds to the Motorola
write of the
PAH
,
PAL
,
PCON
, or
DSCRATCH
register
shown in
Figure 39
. In the figure and in the timing
sequences described below, it is assumed that PIDS is
tied high, selecting an active-low data strobe (PODS).
1. The host drives a valid address onto PADD[3:0] and
drives PRWN low.
2. The host initiates the cycle by asserting (low) PCSN
and PODS.
3. The host drives data onto PD[15:0].
4. If
PDI
is empty, the PIU notifies the host by asserting
PRDY and deasserting PIBF. If
PDI
is still full from a
previous host write, the host must wait until the PIU
asserts PRDY.
5. The host concludes the cycle by deasserting PCSN
or PODS, causing the PIU to latch the data from
PD[15:0] into
PDI
. The PIU transfers the data in
PDI
into
PAH
,
PAL
,
PCON
, or
HSCRATCH
.
6. The host 3-states PD[15:0].
Note:
Once the host initiates a register write transac-
tion, it must complete it properly as described
above. If the host concludes the transaction
before the PIU asserts PRDY, the results are
undefined and the PIU must be reset. In this
case, the host can reset the PIU by setting the
HRESET field (
PCON
[5]—
Table 73 on
page 133
) or a core can reset the PIU by setting
the DRESET field (
PCON
[6]).