Epson S1C33L03 User Manual

III PERIPHERAL BLOCK: SERIAL INTERFACE

B-III-8-12

EPSON

S1C33L03 FUNCTION PART

Asynchronous Interface

Outline of Asynchronous Interface

Asynchronous transfers are performed by adding a start bit and a stop bit to the start and end points of each serial-

converted data. With this method, there is no need to use a clock that is fully synchronized on the transmit and

receive sides; instead, transfer operations are timed by the start and stop bits added to the start and end points of

each data.

In the 8-bit asynchronous mode (SMDx[1:0] = "11"), 8 bits of data can be transferred; in the 7-bit asynchronous

mode (SMDx[1:0] = "10"), 7 bits of data can be transferred.

In either mode, it is possible to select the stop-bit length, add a parity bit, and choose between even and odd parity.

The start bit is fixed at "1".

The operating clock can be selected between an internal clock generated by an 8-bit programmable timer or an

external clock that is input from the #SCLKx pin.

Since the transmit and receive units are both constructed with a double-buffer structure, successive transmit and

receive operations are possible. Furthermore, since the transmit and receive units are independent, full-duplex

communication in which transmit and receive operations are performed simultaneously is also possible.

Figure 8.8 shows an example of how input/output pins are connected for transfers in the asynchronous mode.

Data input

Data output

External clock

SINx

SOUTx

#SCLKx

SINx

SOUTx

External
serial device

(1) When external clock is used

(2) When internal clock is used

S1C33

Data input

Data output

External
serial device

S1C33

Figure 8.8 Example of Connection in Asynchronous Mode

When the asynchronous mode is selected, it is possible to use the IrDA interface function.

Asynchronous-transfer data format

The data format for asynchronous transfer is shown below.

Data length: 7 or 8 bits (determined by the selected transfer mode)

Start bit:

1 bit, fixed

Stop bit:

1 or 2 bits

Parity bit:

Even or odd parity, or none

Sampling clock (for transmitting)

s1: start bit, s2 & s3: stop bit, p: parity bit

7-bit asynchronous mode

(Stop bit: 1 bit, parity: none)

(Stop bit: 1 bit, parity: used)

(Stop bit: 2 bits, parity: none)

(Stop bit: 2 bits, parity: used)

8-bit asynchronous mode

(Stop bit: 1 bit, parity: none)

(Stop bit: 1 bit, parity: used)

(Stop bit: 2 bits, parity: non)

(Stop bit: 2 bits, parity: used)

Figure 8.9 Data Format for Asynchronous Transfer

Serial data is transmitted and received, starting with the LSB.