PX-4 STAT I/O devices

Format: STAT logical:=physical:

The device function of STAT is actually manipulation of the I/O byte at location 0003h in memory. For the PX-4, default values are set with the DIP-switches located in the capsule-ROM compartment.

Devices exist in three types:

• Logical devices - these are functional; input, output, input/output and list device
• Physical devices - an intermediate configuration. The actual implementation differs with the Logical device it is attached to. Not all defined Physical devices are implemented in the BIOS.
• Real devices - hardware and driver.

There are four Logical devices, each with a typical function:

• RDR: input only
• PUN: output only
• CON: input/output
• LST: list device, usually a printer

There are 12 Physical devices, of three types: output, input and both output and input. A Physical device is a configuration of a Real device, which can differ per Logical device. Physical devices can be connected to Real devices, which is some hardware and a driver. Not all Physical devices are actually implemented, but this could be added in the User BIOS.

Each Logical device can have one of a short list of several Physical devices attached. Each Logical/Physical device combination defines a specific Real device.

Log. Phys.  Real                 Phys.  Real               Phys.  Real               Phys.  Real
LST: TTY: = Serial (printer),    CRT: = Cartridge printer, LPT: = RS-232C (printer), UL1: not implemented.
PUN: TTY: not implemented,       PTP: = LCD display,       UP1: = RS-232C out,       UP2: not implemented.
RDR: TTY: = Keyboard,            PTR: not implemented,     UR1: = RS-232C in,        UR2: not implemented.
CON: TTY: = RS232C out/Keyboard, CRT: = LCD/Keyboard,      BAT: = LCD/RS-232C in,    UC1: = RS-232C in/out.

Note the Centronics port of the PX-4 is not even defined as a Physical/Real device in the Operating Manual. The Operating System Reference Manual lists the Centronics port as UL1:

The default for the PX-4 is (STAT DEV:):

CON: is CRT:
RDR: is UR1:
PUN: is UP1:
LST: is UL1:

Sources:

• PX-4 Operating Manual, p.5-32
• PX-4 Operating System Reference Manual II, p. II-365
• CP/M 2.2 Operating System Manual, p.1-16

fjkraan@electrickery, 2026-05-09