HYUNDAI MicroElectronics GMS90X5XC Series
20 Jan. 2001 Ver 1.0
SERIAL INTERFACE (USART)The serial port is full duplex and can operate in four modes (one synchronous mode, three asynchronous modes)
as illustrated in Table 6. The possible baud rates can be calculated using the formulas given in Table 7.
Table 6. USART Operating Modes
Mode SCON Baudrate Description
SM0 SM1
0 0 0 Serial data enters and exits through RxD.
TxD outputs the shift clock. 8-bit are tra nsmit-
ted/received (LSB first)
1 0 1 Timer 1/2 overflow rate 8-bit UART
10 bits are transmitted (through TxD) or
received (RxD)
2 1 0 or 9-bit UART
11 bits are transmitted (TxD) or received (RxD)
3 1 1 Timer 1/2 overflow rate 9-bit UART
Like mode 2 except the variable baud rate
Table 7. Formulas for Calculating Baud rates
Baud Rate
derived from Interface Mode Baudrate
Oscillator 0
2
Timer 1 (16-bit timer)
(8-bit timer with
8-bit auto reload)
1,3
1,3
Timer 2 1,3
f
OSC
12
------------
f
OSC
32
------------
f
OSC
64
------------
f
OSC
12
------------
2
SMOD
64
------------------
f
OSC
×
2
SMOD
32
------------------
Timer 1 overflow
()×
2
SMOD
32
------------------
f
OSC
12 256 TH1
()–[]×
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×
f
OSC
32 65536 RC2H RC 2L
,()–[]×
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