Serial Host Interface (SHI, SHI_1)
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
Freescale Semiconductor
10-15
NOTE
Clearing the HRIE[1:0] bits masks a pending receive interrupt only after a
one instruction cycle delay. If the HRIE[1:0] bits are cleared in a long
interrupt service routine, it is recommended that at least one other
instruction separates the instruction (that clears the HRIE[1:0] bits) and the
RTI instruction at the end of the interrupt service routine.
10.3.8.12 HCSR Host Transmit Underrun Error (HTUE)—Bit 14
The read-only status bit HTUE indicates whether a transmit-underrun error occurred. Transmit-underrun
errors can occur only when operating in the SPI slave mode or the I
2
C slave mode (when HCKFR is
cleared). In master mode, transmission takes place on demand and no underrun can occur. The HTUE bit
is set when both the shift register and the HTX register are empty and the external master begins reading
the next word:
•
When operating in I
2
C mode, the HTUE bit is set on the falling edge of the ACK bit, and the SHI
re-transmits the previously transmitted word.
•
When operating in SPI mode,
— If CPHA = 1, then the HTUE bit is set at the first clock edge.
— If CPHA = 0, then the HTUE bit is set at the assertion of the SS line.
If a transmit interrupt occurs:
•
When the HTUE bit is set, then the transmit-underrun interrupt vector is generated.
•
When the HTUE bit cleared, then the regular transmit-data interrupt vector is generated.
The HTUE bit is cleared by reading the HCSR register and then writing to the HTX register. The HTUE
bit is cleared by hardware, software, and SHI individual resets, and also during the stop state.
Table 10-6. HCSR Receive Interrupt Enable Bits
HRIE[1:0]
Status Bits
Interrupt
00
Disabled
01
If HRNE = 1 and HROE = 0
Receive FIFO is not empty
If HROE = 1
Receive Overrun Error
10
Reserved
11
If HRFF = 1 and HROE = 0
Receive FIFO is full
If HROE = 1
Receive Overrun Error
Содержание Symphony DSP56724
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