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SCI COMMUNICATION BETWEEN ST7 AND PC

Note: ETPR and ERPR can be used to finetune the baud rate. When ETPR and ERPR con-

tain any value other than 0, the BRR register is disabled and the baud rates are given by the

formula:

where EPTR and ERPR = 1 to 255.

3.2.3 Word length

The word length is selected by the M bit in the SCICR1 register.

In the application, data length is always 8 bits, but the user can force a second stop bit. This

data, R8 bit will always be set (reception of 2 stop bits).

Special bits (PCE,PS,PIE) are also available to use the SCI with parity (not used in this appli-

cation). Refer to the datasheet for more information.

3.2.4 Selecting reception and transmission modes

The selection is made using the SCICR2 register.

Transmission is enabled or disabled depending on the value of the TE bit of SCICR2 (TE = 1,

transmission enabled). When disabled, the TDO pin is free for general purpose I/O.

Reception is enabled or disabled depending on the value of the RE bit of SCICR2 (RE = 1, re-

ception enabled). When disabled, the RDI pin is is free for general purpose I/O.

When reception is disabled, no data must be sent to the ST7. If data are to be received at this

time, the RE bit must be set. Otherwise a wrong byte might be detected when going back into

reception mode.

70

R8

T8

SCID

M

WAKE

PCE

PS

PIE

70

TIE

TCIE

RIE

ILIE

TE

RE

RWU

SBK