SLAS191A datasheet(67/86 Pages) TI

67 / 86 page

5–1

5 Half Duplex Monitor Software UART

The Monitor Program provides several functions for handling serial data communications using the RS-232

interface. The user can call these functions by using the associated vectors in the terminal program. Use

the absolute address mode to call these functions. For example, a possible syntax for preparing the half

duplex software UART to receive characters is:

CALL

&0FFD6h

;in address FFD6h the vector of RX_Prep is stored

another possible syntax is:

RX_Prep .equ

0FFD6h

CALL

&RX_Prep ;in address FFD6h the vector of RX_Prep is stored

The STK/EVK software UART cannot be used for binary transfers for the following two reasons:

•

The protocol has only seven data-bits.

•

A zero cannot be received because this is the detection scheme for no-character-received.

The vectors related to these functions are stored in the following locations (see Table 5–1):

Table 5–1. Function/Vector

FUNCTION NAME

VECTOR ADDRESS

FUNCTION PURPOSE

TX_Word

0FFD0h

Transmit 1 space and a four digit hex number in R11

TX_Char†

0FFD2h

Transmit 1 char in TXData (20Eh)

TX_Table†

0FFD4h

Transmit table (string address should be in R11)

RX_Prep†

0FFD6h

Prepare halfduplex software UART for receive

TX_Prep†

0FFD8h

Prepare halfduplex software UART for transmit

INT_RXTX

0FFDAh

Interrupt service routine for receive and transmit

Ret_Mon

0FFDCh

Return to the Monitor with a br Ret_Mon statement

† Calling TX_Char, TX_Table, TX_Prep, or RX_Prep enables the GIE flag in the status register (SR). The GIE bit remains

set even if it was disabled before calling these routines.

5.1

Transmission Parameters of the Software UART

The transmission parameters of the MSP-STK/EVK430x320 and EVK430x330 are:

•

2400 Baud

•

1 start-bit

•

7 data-bits

•

1 parity-bit (even)

•

1 stop-bit

The RTS and DTR pins of the serial port must be set to high to provide the supply voltage for the STK/EVK

if no battery is assembled. This is done automatically in the Windows HyperTerminal program. If other

communication software is used, the specified pin levels must be met.

5.2

Identification of Bit Pattern AA55h

The interrupt service routine INT_RXTX is used for the receive and transmit function. If another INT_RXTX

service routine is being used, the identification bit pattern AA55h must be stored in memory location 3DEh

(5DEh for the MSP430x33x family). Otherwise, the INT_RXTX service routine will never branch program

execution to the vector located in the user interrupt vector table. This pattern remains in memory until it is

changed by the program or the power is switched off.

SLAS191A 데이터시트(PDF) 67 Page - Texas Instruments

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