
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
10-16
Freescale Semiconductor
Serial Host Interface (SHI, SHI_1)
10.3.8.13 HCSR Host Transmit Data Empty (HTDE)—Bit 15
The read-only status bit HTDE indicates whether the HTX register is empty and can be written by the DSP
core.
•
The HTDE bit is set when the data word is transferred from the HTX register to the shift register,
except in SPI master mode when CPHA bit = 0 (see HCKR register).
•
When in SPI master mode with CPHA bit = 0, the HTDE bit is set after the end of the data word
transmission.
•
The HTDE bit is cleared when the DSP writes the HTX register either with write instructions or
DMA transfers.
The HTDE bit is set by hardware, software, and SHI individual resets, and also during the stop state.
10.3.8.14 HCSR Reserved Bits—Bits 23, 18 and 16
These bits are reserved; they read as zero and should be written with zeroes for future compatibility.
10.3.8.15 Host Receive FIFO Not Empty (HRNE)—Bit 17
The read-only status bit HRNE indicates that the Host Receive FIFO (HRX) contains at least one data
word.
•
The HRNE bit is set when the HRX FIFO is not empty.
•
The HRNE bit is cleared when the HRX FIFO is read by the DSP (using read instructions or DMA
transfers), reducing the number of words in the FIFO to zero.
The HRNE bit is cleared during hardware, software, and SHI individual resets, and also during the stop
state.
10.3.8.16 Host Receive FIFO Full (HRFF)—Bit 19
The read-only status bit HRFF indicates, when set, that the Host Receive FIFO (HRX) is full. The HRFF
bit is cleared when the HRX FIFO is read by the DSP (using read instructions or DMA transfers) and at
least one place is available in the HRX FIFO. The HRFF bit is cleared by hardware, software, and SHI
individual resets, and also during the stop state.
10.3.8.17 Host Receive Overrun Error (HROE)—Bit 20
The read-only status bit HROE indicates, when set, that a data-receive overrun error has occurred.
Receive-overrun errors cannot occur when operating in I
2
C master mode, because the clock is suspended
if the receive FIFO is full; nor can receive-overrun errors occur in I
2
C slave mode when the HCKFR bit is
set.
The HROE bit is set when the shift register (IOSR) is filled and ready to transfer the data word to the HRX
FIFO and the FIFO is already full (HRFF bit is set). When a receive-overrun error occurs, the shift register
is not transferred to the HRX FIFO.
•
If a receive interrupt occurs when the HROE bit is set, the receive-overrun interrupt vector is
generated.