AM85C30 datasheet(159/194 Pages) AMD

159 / 194 page

SCC Application Notes

AMD

7–10

Table 7–5. Time Constants for Common Baud Rates

Baud

Divider

Rate

Dec

Hex

38400

0000H

19200

0002H

9600

0006H

4800

000EH

2400

001EH

1200

003EH

600

126

007EH

300

254

00FEH

150

510

01FEH

For 2.4576 MHz Clock, X16 Clock Mode

WR14 selects the baud-rate generator as the

RTxC pin, baud-rate generator disabled,

and internal loopback. The baud-rate generator uses the

RTxC pin as the clock source

and is not enabled at this time because the SCC initialization is not complete.

7.2.3.2

SCC Operating Mode Enables

WR14 enables the baud-rate generator. Bit 0 (LSB) is changed to a ‘1’ to enable the

baud-rate generator; all other bits must maintain the value selected during initialization.

WR3 enables the receiver. Bit 0 (LSB) is changed to a ‘1’ to enable the receiver; all other

bits must maintain the value selected during initialization.

WR5 enables the transmitter. Bit 3 is changed to a ‘1’ to enable the transmitter; all other

bits must maintain the value selected during initialization.

7.2.4

Transmit and Receive Routines

After initialization, and after all enables have been selected, the SCC is ready for commu-

nication. The transmitter buffer and the receive FIFO are empty. The example shown be-

low is coded to transmit and receive characters.

;Transmit a character

TXCHAR:INPUT

RRO

;Read RRO

TEST

BIT2

;Test transmit

buffer empty

TXCHAR;Loop if not empty

OUTPUT CHAR

;Output character to

data port

RET

;Return

;Receive a character

RXCHAR:INPUT

RRO

;Read RRO

TEST

BIT 0 ;Test Receive

buffer

RXCHAR;Loop if not full

INPUT

CHAR

;Input character

from data port

RET

;Return

Figure 7–3. Transmit and Receive Routine

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