System information

Table 6-5. (continued)

Entry Point Function

location 5,6,7 Set to JMP BDOS, which is the primary entry point

to CP/M for transient programs. (0005H: JMP

3C06H + b)

Refer to Section 6.9 for complete details of page zero use. Upon

completion of the initialization, the WBOOT program must branch to the

CCP at 3400H + b to restart the system. Upon entry to the CCP, register C

is set to the drive to select after system initialization. The WBOOT routine

should read location 4 in memory, verify that is a legal drive, and pass it to

the CCP in register C.

CONST You should sample the status of the currently assigned console device and

return 0FFH in register A if a character is ready to read and 00H in register

A if no console characters are ready.

CONIN The next console character is read into register A, and the parity bit is set,

high-order bit, to zero. If no console character is ready, wait until a

character is typed before returning.

CONOUT The character is sent from register C to the console output device. The

character is in ASCII, with high-order parity bit set to zero. You might

want to include a time-out on a line-feed or carriage return, if the console

device requires some time interval at the end of the line (such as a TI

Silent 700 terminal). You can filter out control characters that cause the console

device to react in a strange way (CTRL-Z causes the Lear-Siegler terminal

to clear the screen, for example).

LIST The character is sent from register C to the currently assigned listing

device. The character is in ASCII with zero parity bit.

PUNCH The character is sent from register C to the currently assigned punch

device. The character is in ASCII with zero parity.

READER The next character is read from the currently assigned reader device into

condition is reported by returning an ASCII CTRL-Z(1AH).

6.6 BIOS Entry Points CP/M Operating System Manual

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