User manual

Monitor12 (MON12) User Manual 05/30/01

I/O ROUTINES

The I/O section of the main module consists of a set of supervisor routines, and

three sets of driver routines. The supervisor routines are INIT, INPUT, and

OUTPUT. These routines determine which driver subroutine to call to perform the

specific action. Each set of driver routines consists of an initialization

routine, an input routine, and an output routine. One set of drivers is for the

SCI port and these routines are called ONSCI, INSCI, and OUTSCI.

All I/O communications are controlled by three RAM locations (IODEV, EXTDEV, and

HOSTDEV). EXTDEV specifies the external device type (0=none, l=SCI1). HOSTDEV

specifies which I/O port is used for host communications (O=SCI, 1=SCI1). IODEV

instructs the supervisor routine which port/driver routine to use (0=SCI,

1=SCI1).

The INIT routines set up a serial transmission format of eight data bits, two

stop bits, and no parity. For the SCI, the baud rate is set to 9600 for a 16MHz

crystal (8MHz E-clock). To achieve a different baud rate the baud rate control

registers can be modified using the MM command. For the SCI, this means

modifying the SCOBDH and SCOBDL registers (refer to MCU data sheet, SCI baud

rate selection).

The INPUT routine reads from the specified port. If a Character is received,

the character is returned in accumulator A. If no character is received a zero

(0) is returned in accumulator A. This routine does not wait for a character to

be received before returning (this function performed by the INCHAR subroutine).

The OUTPUT routine takes the ASCII character loaded in accumulator A and writes

to the specified I/O port. This routine waits until the character is

transmitted before returning.

UTILITY SUBROUTINES

Several subroutines exist that are available for performing I/O tasks. A jump

table has been set up in ROM directly beneath the interrupt vectors. To use

these subroutines, execute a jump to subroutine (JSR) command to the appropriate

entry in the jump table. By default, all I/O performed with these routines is

sent to the terminal port. Redirection of the I/O port is achieved by placing

the specified value (O=SCI, 1=SCI1) into RAM location IODEV.

Utility subroutines available to the user are as follows:

UPCASE If character in accumulator A is lower case alpha, convert to upper

case.

WCHEK Test character in accumulator A and return with Z bit set if

character is white space (space, comma, tab).

DCHEK Test character in accumulator A and return with Z bit set if

character is delimiter (carriage return or white space).

INIT Initialize I/O device.

INPUT Read I/O device.

OUTPUT Write I/O device.