Samsung KS57C2308 Manual page 275

KS57C2308/P2308/C2316/P2316
SERIAL I/O MODE REGISTER (SMOD)
The serial I/O mode register, SMOD, is an 8-bit register that specifies the operation mode of the serial interface.
Its reset value is logical zero. SMOD is organized in two 4-bit registers, as follows:
FE0H SMOD.3
FE1H SMOD.7
SMOD register settings enable you to select either MSB-first or LSB-first serial transmission, and to operate in
transmit-and-receive mode or receive-only mode. SMOD is a write-only register and can be addressed only by
8-bit RAM control instructions. One exception to this is SMOD.3, which can be written by a 1-bit RAM control
instruction. When SMOD.3 is set to 1, the contents of the serial interface interrupt request flag, IRQS, and the
3-bit serial clock counter are cleared, and SIO operations are initiated. When the SIO transmission starts,
SMOD.3 is cleared to logical zero.
SMOD.0 0
1
SMOD.1 0
1
SMOD.2 0
1
SMOD.3
1
SMOD.4
0
SMOD.7 SMOD.6
0 0
0 0
0 1
1 0
1 1
NOTES:
1. "fxx" = system clock.
2. kHz frequency ratings assume a system clock (fxx) running at 4.19 MHz.
3. The SIO clock selector circuit cannot select a fxx/2
SMOD.2 SMOD.1
SMOD.6 SMOD.5
Table 13-1. SIO Mode Register (SMOD) Organization
Most significant bit (MSB) is transmitted first
Least significant bit (LSB) is transmitted first
Receive-only mode; output buffer is off
Transmit-and-receive mode; output buffer is on
Disable the data shifter and clock counter; retain contents of IRQS flag when serial
transmission is halted
Enable the data shifter and clock counter; set IRQS flag to "1" when serial
transmission is completed
Clear IRQS flag and 3-bit clock counter to "0"; initiate transmission and then reset
this bit to logic zero
Bit not used; value is always "0"
SMOD.5
0 External clock at
1 Use TOL0 clock from TC0
– CPU clock: fxx/4, fxx/8, fxx/64
0
4.09 kHz clock: fxx/2
1
262 kHz clock: fxx/2
4
SMOD.0
0
Clock Selection
pin
SCK
10
4
clock if the CPU clock is fxx/64
SERIAL I/O INTERFACE
R/W Status of SBUF
SBUF is enabled when SIO
operation is halted or when
goes high.
Enable SBUF read/write
SBUF is enabled when SIO
operation is halted or when
goes high.
.
SCK
SCK
13-3