Host Wait Feedback Strobe (Hwait) - Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual

Host Wait Feedback Strobe (HWAIT)

The feedback strobe is a handshake signal that is used to hold off
HWAIT
the host device from sending further data while the boot kernel is busy.
This is especially critical when processing initialization code or zero-filling
memory where the boot kernel may not be ready for additional data. It is
used primarily for slave boot modes, such as with the UART and SPI slave
modes, but is available to all boot modes.
The strobe does not stick to a certain pin. Rather, any of the 48
HWAIT
GPIOs can be used for this purpose. The flag word of the first block in the
boot stream tells the boot kernel which GPIO to use. The 2-bit field
enables the
PPORT
strobe operates at port F, G, or H. See
bit settings.
The 4-bit field
determines which GPIO pin of the chosen port is used to handshake with
the host. For example, if
strobe is activated on
For individual boot modes, certain GPIOs on port F cannot be used for
functionality as they are used for other purposes.
HWAIT
how the port function enable and muxing registers are programmed at
boot time.
To specify which GPIO is to be used as the
switch in the VisualDSP++ loader options property page. For example, to
use as
PG13 HWAIT
page write:
-pflag PG13
The switch
-pflag
number of the GPIO in the corresponding port, for example,
ADSP-BF537 Blackfin Processor Hardware Reference
functionality and determines whether the
HWAIT
(also shown in
PFLAG
=b#10 and
PPORT
.
PG6
, in the additional options tab of the loader property
takes as an argument
System Reset and Booting
Figure 19-6 on page 19-14
Figure 19-6 on page
=b#0110 then
PFLAG
signal use the
HWAIT
, , or
PF# PG# PH#
HWAIT
for the
19-14) then
HWAIT
Table 19-3 shows
-PFLAG
, where is the
#
.
PG10
19-19