User's Manual

PMAC User Manual
Talking to PMAC 27
PC Bus Interface
The PC bus interface for the PMAC PC and the PMAC Lite can work with just the PC-XT bus (eight bits
wide). The additional AT-bus connecter is provided, but it can only be used to access the additional AT
interrupt lines. One PMAC occupies 16 addresses in the PC’s port I/O space. The base address of this
space is determined by jumpers E91-E92 and E66-E71. Of course, the address should be chosen so as not
to conflict with anything else in the PC. The factory default setting is for address 528 (210 hex). The
Jumper Description section contains a thorough mapping of a typical PC’s I/O mapping and likely empty
addresses.
Characters are passed one at a time through one of these addresses. The software to support this interface
is very similar to that for the serial port. Of course, characters can be sent much faster over the bus port.
The Option 2 dual-ported RAM board provides 8k x 16 bits of shared memory for passing data back and
forth between PMAC and the host computer. The data path for this memory is 16 bits wide, and so
supports the AT bus directly.
STD Bus Interface
The bus interface for the PMAC STD works virtually identically to the PC bus interface on the PMAC PC
or Lite. The interface can work with either the original 8-bit STD bus, or the new 32-bit STD 32 bus. It
occupies 16 words in the I/O space of the host computer. The base address of these 16 words is
determined using jumpers W11-W22 on the baseboard of the PMAC STD. The factory default setting is
for address 61,584 (F090 hex). The Jumper Description section contains a thorough mapping of a typical
STD bus computer's I/O mapping and likely empty addresses.
The new PMAC1.5 STD does not support the 32-bit features of STD 32, although it will work in either
STD 80 or STD 32 buses with 16-bit addressing. On the PMAC 1.5 STD, the DIP switch bank S1-1 to
S1-12 controls the address of the board on the STD bus.
VME Bus Interface
The PMAC VME interfaces to the VME bus as a slave device. Commands and responses are sent
through a set of 16 8-bit mailbox registers. Binary data can be passed through the on-board Option 2V
dual-ported RAM (8k x 16 bits). The data bus is eight bits wide for the mailbox, and 16 bits wide for the
DPRAM. The address bus can be configured for 16, 24, or 32 bits. The address and nature of this
interface must be set up through the serial port by writing to registers in PMAC, saving the values to non-
volatile memory, and resetting the card. Typically, for this model of board, the initial setup and
development is done through the serial port with an IBM-PC or compatible, using the supplied PMAC
Executive program. Instructions for setting up the VME bus interface are given in the Writing a Host
Communications Program section of this manual.
Giving Commands to PMAC
PMAC is fundamentally a command-driven device, unlike other controllers that are register driven.
PMAC will do things if it is issued ASCII command text strings. Generally, PMAC provides information
to the host in ASCII text strings.
PMAC Processing of Commands
When PMAC receives an alphanumeric text character over one of its ports, it does nothing but place the
character in its command queue. It requires a control character (ASCII value 1 to 31) to cause it to take
some actual action. The most common control character used is the carriage return (<CR>; ASCII value
13), which tells PMAC to interpret the preceding set of alphanumeric characters as a command and to
take the appropriate action.