ADSP-BF537 Blackfin Processor Hardware Reference
19-19
System Reset and Booting
Host Wait Feedback Strobe (HWAIT)
The
HWAIT
feedback strobe is a handshake signal that is used to hold off
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
HWAIT
strobe does not stick to a certain pin. Rather, any of the 48
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
PPORT
enables the
HWAIT
functionality and determines whether the
HWAIT
strobe operates at port F, G, or H. See
bit settings.
The 4-bit field
PFLAG
(also shown in
determines which GPIO pin of the chosen port is used to handshake with
the host. For example, if
PPORT
=b#10 and
PFLAG
=b#0110 then
HWAIT
strobe is activated on
PG6
.
For individual boot modes, certain GPIOs on port F cannot be used for
HWAIT
functionality as they are used for other purposes.
how the port function enable and muxing registers are programmed at
boot time.
To specify which GPIO is to be used as the
HWAIT
signal use the
-PFLAG
switch in the Vi+ loader options property page. For example, to
use
PG13
as
HWAIT
, in the additional options tab of the loader property
page write:
-pflag PG13
The switch
-pflag
takes as an argument
PF#
,
PG#
, or
PH#
, where
#
is the
number of the GPIO in the corresponding port, for example,
PG10
.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...