
Synchronous Serial Interface (SSI)
Freescale Semiconductor
24-9
24.3.2
SSI Transmit FIFO 0 and 1 Registers
The SSI transmit FIFO registers are 8x32-bit registers. These registers are not directly accessible. The
transmit shift register (TXSR) receives its values from these FIFO registers. When the transmit interrupt
enable (SSI_IER[TIE]) bit and either of the transmit FIFO empty (SSI_ISR[TFE0, TFE1]) bits are set, an
interrupt is generated when the data level in of the SSI transmit FIFOs falls below the selected threshold.
24.3.3
SSI Transmit Shift Register (TXSR)
TXSR is a 24-bit shift register that contains the data transmitted and is not directly accessible. When a
continuous clock is used, the selected bit clock shifts data out to the SSI_TXD pin when the associated
frame sync is asserted. When a gated clock is used, the selected gated clock shifts data out to the SSI_TXD
port.
The word length control bits (SSI_CCR[WL]) determine the number of bits to shift out of the TXSR before
it is considered empty and can be written to again. The data to be transmitted occupies the most significant
portion of the shift register if SSI_TCR[TXBIT0] is cleared. Otherwise, it occupies the least significant
portion. The unused portion of the register is ignored.
NOTE
If TXBIT0 is cleared and the word length is less than 16 bits, data occupies
the most significant portion of the lower 16 bits of the transmit register.
When SSI_TCR[SHFD] is cleared, data is shifted out of this register with the most significant bit (msb)
first. If this bit is set, the least significant bit (lsb) is shifted out first. The following figures show the
transmitter loading and shifting operation. They illustrate some possible values for WL, which can be
extended for the other values.
Figure 24-5. Transmit Data Path (TXBIT0=0, TSHFD=0) (msb Alignment)
SSI_TX
31
0
24 bits
20 bits
16 bits
31
0
TXSR
15 11
7
12 bits
12 bits
16 bits
SSI_TXD
MCF5329 Reference Manual, Rev 3
Содержание MCF5329
Страница 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 126: ...Enhanced Multiply Accumulate Unit EMAC 4 20 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
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Страница 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
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Страница 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 692: ...Programmable Interrupt Timers PIT0 PIT3 28 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 720: ...Queued Serial Peripheral Interface QSPI 30 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
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Страница 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 902: ...Register Memory Map Quick Reference A 26 Freescale Semiconductor MCF5329 Reference Manual Rev 3...