30-20
MC9328MX1 Reference Manual
MOTOROLA
Synchronous Serial Interface (SSI)
When the SSI is configured as an I
2
S master, the external codec may require an oversampling clock in
addition to the sampling rate frequency and bit clock. This oversampling clock is usually required to be
256 times the sampling frequency.
As an example, if a sampling frequency of 44.1 kHz was required, and the word length was set to 16-bits.
Then a frame sync would be 2
×
16 = 32 bit clocks. This makes the bit clock frequency 1.4112 MHz.
The frequency ratios that must hold would be the following:
SYS_CLK (PerCLK3) = 256
×
Frame Sync
Eqn. 30-1
Frame_Sync = Bit Clock / 32
Eqn. 30-2
Therefore,
SYS_CLK (PerCLK3) = 8
×
Bit Clock
Eqn. 30-3
If the divide ratio is set to 8—that is, PM = 1 and PSR = 0, SYS_CLK_EN is set, the module is in I
2
S
master mode and the incoming frequency of PerCLK3 is 11.2896 MHz, then SYS_CLK will meet the
requirements. The external codec will not need a crystal oscillator for clocking.
30.3.8 SSI Transmit Configuration Register
The SSI Transmit Configuration Register (STCR) controls the transmit operation of the SSI. This register
controls the frame synchronization signal, clocking, and data direction. It also contains enables for the
DMA, transmit FIFO, and the transmit interrupt.
As with all on-chip peripheral interrupts for the MC9328MX1, the STCR must first be set to enable
maskable interrupts. Next, the AITC (ARM9 Interrupt Controller) is configured to handle the SSI
interrupts. For example, the SSI interrupt bits (bits 45 through 42) in the AITC’s Interrupt Enable High
Master or save
RSCKP
SRCR [3]
1
Rising edge of bit clock clocks data in
Master or save
TFSI
STCR [2]
1
Transmit frame sync is active low
Master or save
RSFI
SRCR [2]
1
Receive frame sync is active low
Master or save
TFSL
STCR [1]
0
Transmit frame sync length is 1 word
Master or save
RFSL
SRCR [1]
0
Receive frame sync length is 1 word
Master or save
TEFS
STCR [0]
1
Transmit frame sync initiated sync one
bit-clock before transmission
Master or save
REFS
SRCR [0]
1
Receive frame sync initiated one bit-clock
before receive
Master
TXDIR
STCR [5]
1
Clock source is generated internally bit clock
Master
TFDIR
STCR [6]
1
Transmit frame sync is generated internally
Slave
TXDIR
STCR [5]
0
Clock source is externally generated bit clock
Slave
TFDIR
STCR [6]
0
Transmit frame sync is generated externally
Table 30-9. I
2
S Master or I
2
S Slave Mode Settings (Continued)
I
2
S Mode
Bit
Name
Register
Location
Forced
Value
Function
Summary of Contents for DragonBall MC9328MX1
Page 68: ...1 12 MC9328MX1 Reference Manual MOTOROLA Introduction ...
Page 86: ...2 18 MC9328MX1 Reference Manual MOTOROLA Signal Descriptions and Pin Assignments ...
Page 116: ...3 30 MC9328MX1 Reference Manual MOTOROLA Memory Map ...
Page 126: ...4 10 MC9328MX1 Reference Manual MOTOROLA ARM920T Processor ...
Page 160: ...8 8 MC9328MX1 Reference Manual MOTOROLA System Control ...
Page 272: ...13 32 MC9328MX1 Reference Manual MOTOROLA DMA Controller ...
Page 281: ...Programming Model MOTOROLA Watchdog Timer Module 14 9 ...
Page 282: ...14 10 MC9328MX1 Reference Manual MOTOROLA Watchdog Timer Module ...
Page 300: ...15 18 MC9328MX1 Reference Manual MOTOROLA Analog Signal Processor ASP ...
Page 438: ...18 16 MC9328MX1 Reference Manual MOTOROLA Serial Peripheral Interface Modules SPI 1 and SPI 2 ...
Page 478: ...19 40 MC9328MX1 Reference Manual MOTOROLA LCD Controller ...
Page 574: ...21 32 MC9328MX1 Reference Manual MOTOROLA Memory Stick Host Controller MSHC Module ...
Page 598: ...23 16 MC9328MX1 Reference Manual MOTOROLA Real Time Clock RTC ...
Page 670: ...24 72 MC9328MX1 Reference Manual MOTOROLA SDRAM Memory Controller ...
Page 726: ...25 56 MC9328MX1 Reference Manual MOTOROLA SmartCard Interface Module SIM ...
Page 736: ...26 10 MC9328MX1 Reference Manual MOTOROLA General Purpose Timers ...
Page 854: ...29 18 MC9328MX1 Reference Manual MOTOROLA I2C Module ...
Page 900: ...30 46 MC9328MX1 Reference Manual MOTOROLA Synchronous Serial Interface SSI ...
Page 942: ...32 26 MC9328MX1 Reference Manual MOTOROLA GPIO Module and I O Multiplexer IOMUX ...