ADSP-BF537 Blackfin Processor Hardware Reference
10-25
SPI Compatible Port Controllers
If the transmit buffer remains empty or the receive buffer remains full, the
device operates according to the states of the
SZ
and
GM
bits in
SPI_CTL
. If
SZ = 1
and the transmit buffer is empty, the device repeatedly transmits 0s
on the
MOSI
pin. One word is transmitted for each new transfer initiate
command. If
SZ = 0
and the transmit buffer is empty, the device repeat-
edly transmits the last word it transmitted before the transmit buffer
became empty. If
GM = 1
and the receive buffer is full, the device contin-
ues to receive new data from the
MISO
pin, overwriting the older data in
the
SPI_RDBR
buffer. If
GM = 0
and the receive buffer is full, the incoming
data is discarded, and
SPI_RDBR
is not updated.
Transfer Initiation From Master (Transfer Modes)
When a device is enabled as a master, the initiation of a transfer is defined
by the two
TIMOD
bits of
SPI_CTL
. Based on those two bits and the status of
the interface, a new transfer is started upon either a read of
SPI_RDBR
or a
write to
SPI_TDBR
.
L
If the SPI port is enabled with
TIMOD
=
01
or
TIMOD
=
11
, the hard-
ware immediately issues a first interrupt or DMA request.
Table 10-4. Transfer Initiation
TIMOD
Function
Transfer Initiated Upon
Action, Interrupt
00
Transmit and
Receive
Initiate new single word trans-
fer upon read of SPI_RDBR
and previous transfer com-
pleted.
Interrupt active when receive
buffer is full.
Read of SPI_RDBR clears
interrupt.
01
Transmit and
Receive
Initiate new single word trans-
fer upon write to SPI_TDBR
and previous transfer com-
pleted.
Interrupt active when transmit
buffer is empty.
Writing to SPI_TDBR clears
interrupt.
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 ...