Data Sheet
June 2001
DSP16410B Digital Signal Processor
148
Agere Systems—Proprietary
Use pursuant to Company instructions
Agere Systems Inc.
4 Hardware Architecture
(continued)
4.15 Parallel Interface Unit (PIU)
(continued)
4.15.5 Host Commands
(continued)
4.15.5.5 Memory Write Commands
The DMAU
1
coordinates and executes host data write commands via its PIU bypass channel (
Section 4.13.4 on
page 85
). Prior to issuing a data write command, the host must initialize the
PA
register with the starting address in
memory by executing the
write_pah
and
write_pal
commands.
Table 87
describes each host write command in
detail.
Table 87. Memory Write Commands
4.15.5.6 Flow Control for Control/Status/Address Register and Memory Write Commands
The host must use proper flow control for write commands (
write_pdi
,
write_pdi++
,
write_pah
,
write_pal
,
write_pcon
, or
write_hscratch
) using one of two methods:
1. After the host initiates a write cycle, it can monitor the PRDY pin to determine if
PDI
is already full. If so, the host
can extend the access and wait for the PIU to assert PRDY.
2. If the host is unable to use the PRDY pin for flow control, it can monitor the PIBF field (
PCON
[1]—see
Table 73
on page 133
) before initiating the transaction. For example, the host can execute the following pseudocode:
Do:
Issue a read_pcon command to the core
Repeat until PIBF = = 0
Issue the write_pdi command
// Host read of PCON.
// Wait for PIBF = 0.
// Write word into PDI.
1. A core can coordinate host data read commands by program control, but this is very inefficient compared to using the DMAU for this pur-
pose.
Command
Mnemonic
write_pdi
Description
This command causes the PIU to:
Latch the data from PD[15:0] into
PDI
.
Request the DMAU to write the contents of
PDI
to the single word pointed to by the contents of
PA
.
The host must use proper flow control with this command (see
Section 4.15.5.6
).
This command causes the PIU to:
write_pdi++
Latch the data from PD[15:0] into
PDI
.
Request the DMAU to write the contents of
PDI
to the single word pointed to by the contents of
PA
.
Postincrement the address in
PA
to point the next single-word location.
The host must use proper flow control with this command (see
Section 4.15.5.6
).