Samsung KS57C2308 Serial I/O Buffer Register Sbuf, SBUF,EA EA,#0EEH SMOD,EA, Bitr EMB EA,TDATA

KS57C2308/P2308/C2316/P2316 SERIAL I/O INTERFACE

SERIAL I/O BUFFER REGISTER (SBUF)

The serial I/O buffer register, SBUF, can be read or written using 8-bit RAM control instructions. Following a RESET, the value of SBUF is undetermined.

When the serial interface operates in transmit-and-receive mode (SMOD.1 = "1"), transmit data in the SIO buffer register are output to the SO pin (P0.2) at the rate of one bit for each falling edge of the SIO clock. Receive data are simultaneously input from the SI pin (P0.3) to SBUF at the rate of one bit for each rising edge of the SIO clock. When receive-only mode is used, incoming data are input to the SIO buffer at the rate of one bit for each rising edge of the SIO clock.

+PROGRAMMING TIP — Setting Transmit/Receive Modes for Serial I/O

1.Transmit the data value 48H through the serial I/O interface using an internal clock frequency of fxx/24 and in MSB-first mode:

BITS	EMB
SMB	15
LD	EA,#48H	;
LD	SBUF,EA	;
LD	EA,#0EEH
LD	SMOD,EA	; SIO data transfer

SCK / P0.1

SO / P0.2

EXTERNAL

DEVICE

KS57C2308/C2316

2. Use CPU clock to transfer and receive serial data at high speed:

BITR	EMB
LD	EA,TDATA	; TDATA address = BANK0 (20H–7FH)
LD	SBUF,EA
LD	EA,#4FH
LD	SMOD,EA	; SIO start
BITS	IES
STEST BTSTZ	IRQS
JR	STEST
LD	EA,SBUF
SMB	0
LD	RDATA,EA	; RDATA address = BANK0 (20H–7FH)

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