Samsung KS57C2308 Manual page 277

KS57C2308/P2308/C2316/P2316
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
, the value of SBUF is undetermined.
RESET
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/2
and in MSB-first mode:
BITS
SMB
LD
LD
LD
LD
2. Use CPU clock to transfer and receive serial data at high speed:
BITR
LD
LD
LD
LD
BITS
STEST BTSTZ
JR
LD
SMB
LD
EMB
15
EA,#48H
SBUF,EA
EA,#0EEH
SMOD,EA
SCK
/ P0.1
SO / P0.2
KS57C2308/C2316
EMB
EA,TDATA
SBUF,EA
EA,#4FH
SMOD,EA
IES
IRQS
STEST
EA,SBUF
0
RDATA,EA
;
;
; SIO data transfer
EXTERNAL
DEVICE
; TDATA address = BANK0 (20H–7FH)
; SIO start
; RDATA address = BANK0 (20H–7FH)
SERIAL I/O INTERFACE
4
13-5