KS57C2308/P2308/C2316/P2316 MEMORY MAP
4-27
SMOD — Serial I/O Mode Register FE1H, FE0H
Bit 76543210
Identifier .7 .6 .5 "0" .3 .2 .1 .0
RESET Value 00000000
Read/Write WWWWR/W W W W
Bit Addressing 88881/8 888
.7–.5 Serial I/O Clock Selection and SBUF R/W Status Control Bits
000Use an external clock at the SCK pin;
Enable SBUF when SIO operation is halted or when SCK goes high
001Use the TOL0 clock from timer/counter 0;
Enable SBUF when SIO operation is halted or when SCK goes high
01xUse the selected CPU clock (fxx/4, 8, or 64; “fxx” is the system
clock); Enable SBUF read/write operation. “x” means “don't care.”
1004.09 kHz clock (fxx/210)
111262 kHz clock (fxx/24); Note: You cannot select a fxx/24 clock
frequency if you have selected a CPU clock of fxx/64
NOTE: All kHz frequency ratings assume a system clock of 4.19MHz
.4 Bit 4
0Always logic zero
.3 Initiate Serial I/O Operation Bit
1Clear IRQS flag and 3-bit clock counter to logic zero; then initiate serial
transmission. When SIO transmission starts, this bit is cleared by hardware to
logic zero
.2 Enable/Disable SIO Data Shifter and Clock Counter Bit
0Disable the data shifter and clock counter; the contents of IRQS flag is
retained when serial transmission is completed
1Enable the data shifter and clock counter; The IRQS flag is set to logic one
when serial transmission is completed
.1 Serial I/O Transmission Mode Selection Bit
0Receive-only mode; output buffer is off
1Transmit-and-receive mode; output buffer is on
.0 LSB/MSB Transmission Mode Selection Bit
0Transmit the most significant bit (MSB) first
1Transmit the least significant bit (LSB) first