
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
2-12
Freescale Semiconductor
Signal Descriptions
HREQ
Input or
Output
Input, Output,
or
Disconnected
Tri-stated
SHI_1’s Host Request
When configured for SPI master mode, this signal is an active low Schmitt-trigger
input. When asserted by the external slave device, HREQ will trigger the start of the
data word transfer by the master. After finishing the data word transfer, the master
will await the next assertion of HREQ to proceed to the next transfer. This pin can
also be programmed as GPIO.
When configured for SPI slave mode, this signal is an active low output. HREQ is
asserted to indicate that the SHI is ready for the next data word transfer; HREQ is
de-asserted at the first clock pulse of the new data word transfer.
PH4
Port H4
When HREQ is configured as GPIO, this signal is individually programmable as
input, output, or internally disconnected.
This signal is tri-stated during hardware, software and individual reset, or when the
HREQ1-HREQ0 bits in the HCSR are cleared. There is no need for an external
pull-up in this state.
This pin is shared by SHI and SHI_1 in DSP56725 80-pin and DSP56724 144-pin
packages.
Uses an internal pull-up resistor.
Table 2-12. Serial Host Interface Signals (SHI_1)
Signal
Name
Signal Type
State
during
Reset
Description
SS_1
Input
Tri-stated
SHI_1’s SPI Slave Select
When configured for SPI_1 Slave mode, SS_1 is used to enable the SPI_1 slave
for transfer, and is an active low Schmitt-trigger input.
When configured for SPI_1 master mode, SS_1 should be kept de-asserted
(pulled high). If SS is asserted while configured in SPI_1 master mode, a bus
error condition is flagged. If SS_1 is de-asserted while configured in SPI_1
master mode, the SHI_1 ignores SCK_1 clocks and keeps the MISO_1 output
signal in the high-impedance state
HA2_1
Input
SHI_1’s I
2
C Slave Address 2
When configured for I
2
C slave mode, HA2_1 is used to form the slave device
address, and is a Schmitt-trigger input.
When configured for I
2
C master mode, HA2_1 is ignored.
This signal is tri-stated during hardware, software and individual reset. Thus,
there is no need for an external pull-up resistor in this state.
Uses an internal pull-up resistor.
Table 2-11. Serial Host Interface Signals (SHI) (Continued)
Signal
Name
Signal Type
State
During
Reset
Description