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Inside Macintosh: Operating System Utilities /

Chapter 7 - Parameter RAM Utilities / Parameter RAM Utilities Reference

Data Structures

The System Parameters Record

The SysParmType data type describes a system parameters record.

TYPE SysParmType =
PACKED RECORD
   valid:      Byte;    {validity status}
   aTalkA:     Byte;    {node ID hint for modem port}
   aTalkB:     Byte;    {node ID hint for printer port}
   config:     Byte;    {use types for serial ports}
   portA:      Integer; {modem port configuration}
   portB:      Integer; {printer port configuration}
   alarm:      LongInt; {alarm setting}
   font:       Integer; {application font number minus 1}
   kbdPrint:   Integer; {printer connection, auto-key settings}
   volClik:    Integer; {caret blink, double click, speaker vol.}
   misc:       Integer; {menu blink, startup disk, mouse scaling }
END;
SysPPtr = ^SysParmType;

Field Description

valid

Contains information about the validity status of the clock chip. Whenever a write to the clock chip is successful, the value $A8 is stored in this field. The status is examined when the clock chip is read at system startup.

aTalkA

Contains the node ID hint for the modem port.

aTalkB

Contains the node ID hint for the printer port.

config

Indicates which device or devices may use each of the serial ports.

portA

Contains the baud rate, data bits, parity, and stop bits for the modem port. Bits 0-9 define the baud rate; bits 10 and 11 define the number of data bits; bits 12 and 13 define the parity; and bits 14 and 15 define the number of stop bits.

portB

Contains the baud rate, data bits, parity, and stop bits for the printer port. Bits 0-9 define the baud rate; bits 10 and 11 define the number of data bits; bits 12 and 13 define the parity; and bits 14 and 15 define the number of stop bits.

alarm

Contains the time at which the alarm clock should sound. The time is defined in terms of seconds since midnight, January 1, 1904.

font

Adding 1 to this field produces the font number of the default application font.

kbdPrint

Contains the settings for the printer and for the keyboard. Bit 0 designates whether the currently chosen printer (if any) is connected to the printer port (0) or the modem port (1). Bits 1-7 are reserved for future use. Bits 8-11 of this field contain the auto-key rate, whose value is stored in 2-tick units. Bits 12-15 contain the auto-key threshold, whose value is stored in 4-tick units.

volClik

Contains miscellaneous user settings, including the caret-blink time, double-click time, and the speaker volume setting.

misc

Contains more miscellaneous user settings. Bits 2 and 3 contain a value from 0 to 3 designating the menu-blink time. Because system software automatically calls both standard and nonstandard menu definition procedures many times, you should not need to worry about that value in parameter RAM. Bit 4 indicates whether the preferred startup disk is in an internal (0) or external (1) drive. If there is any problem with using the disk in the specified drive, the other drive is used. Bit 6 designates whether mouse scaling is on (1) or off (0).