Samsung S3C2451X User Manual page 673

S3C2451X RISC MICROPROCESSOR
MASTER/SLAVE MODE
Master or slave mode can be chosen by setting IMS bit of IISMOD register. In master mode, I2SSCLK and
I2SLRCLK are generated internally and supplied to external device. Therefore a root clock is needed for
generating I2SSCLK and I2SLRCLK by dividing. The IIS pre-scaler (clock divider) is employed for generating a
root clock with divided frequency from internal system clock(PCLK, divided EPLL clock , EPLLrefCLK) and
external I2S clock(from I2SCDCLK pad). The I2SSCLK and I2SLRCLK are supplied from the pin (GPIOs) in slave
mode.
Master/Slave mode is different with TX/RX. Master/Slave mode presents the direction of I2SLRCLK and
I2SSCLK. It doesn't matter the direction of I2SCDCLK (This is only auxiliary.) At slave mode, I2SCDCLK can be
also going out for external IIS codec chip operation. If IIS bus interface transmits clock signals to IIS codec, IIS
bus is master mode. But if IIS bus interface receives clock signal from IIS codec, IIS bus is slave mode. TX/RX
mode indicates the direction of data flow. If IIS bus interface transmits data to IIS codec, this is TX mode.
Conversely, IIS bus interface receives data from IIS codec that is RX mode. Let's distinguish Master/Slave mode
from TX/RX mode.
Figure 26-2 shows the route of the root clock with internal master(PCLK, divided EPLL clock , EPLLRefClock) or
external master(External I2S clock) mode setting in IIS clock control block and system controller. Note that RCLK
indicates root clock and this clock can be supplied to external IIS codec chip at internal master mode and slave
mode.(when CDCLKCON bit of IISMOD register is 1). At slave mode RCLK doesn't affect to I2SSCLK and
I2SLRCLK, but for correct I2S functioning setting RFS, BFS are needed.
System
Controlller
divided
EPLL clock
CLKAUDIO
EPLL
RefCLK
SELI2S
External I2S Clock
DMA Transfer
In the DMA transfer mode, the transmitter or receiver FIFO are accessible by DMA controller. DMA service
request is activated internally by the transmitter or receiver FIFO state. The FTXEMPT, FRXEMPT, FTXFULL,
and FRXFULL bits of I2SCON register represent the transmitter or receiver FIFO data state. Especially,
FTXEMPT and FRXFULL bit are the ready flag for DMA service request; the transmit DMA service request is
activated when TXFIFO is not empty and the receiver DMA service request is activated when RXFIFO is not full.
The DMA transfer uses only handshaking method for single data. Note that during DMA acknowledge activation,
the data read or write operation should be performed.
* DMA request point
- TX mode : ( FIFO is not full ) & ( TXDMACTIVE is active )
- RX mode : ( FIFO is not empty ) & ( RXDMACTIVE is active )
* Note : It only supports single transfer in DMA mode.
IIS
PCLK
I2SAudioCLK
1/N
Pre-scaler
IMS
Figure 26-2. IIS Clock Control Block Diagram
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
1/M
RCLK
CODCLKO
IIS MULTI AUDIO INTERFACE
BCLKmaster
CDCLKCON
PAD
I2SCDCLK
26-3