Rotating Memory Processor (Rmp); Input/Output Processor (Lop) Fundamentals; Command List; Operational Iocd - Xerox 560 Reference Manual

4.
Each unit-record controller (internal or external)
requires one I/O subchannel per each unit record de-
vice attached, up to a maximum of eight.
5.
The maximum number of internal device controllers
within an MIOP is eight (where a unit-record device
controller is equivalent to one, regardless of the
number of assigned subchannels).
6. Any I/O subchannel not assigned to an internal device
controller may be assigned to an external device con-
troller. Thus, if an MIOP has no internal device con-
troller, all 16 I/O subchannels may be assigned to
external device controllers.
ROTATING MEMORY PROCESSOR (RMP)
Each RMP is a speci_al purpose, single-channel lOP designed
to enhance high-speed data transfers between main memory
and anyone of up to eight disk units. Functionally, an
RMP is comparable to an MIOP, except: (1) at any given
time, only one disk unit may be selected for a data transfer
operation, . (2) data transfer rate of disk units are generally
higher than data transfer rates of I/O devices attached to
an MIOP, and (3) the device controller function is per-
formed by the RMP, hence disk units are connected directly
to the RMP rather than via a device controller. (Note:
Although only one disk unit may be actively transferdng
data at any given time, the other units may be active in
performing control functions, e. g., seeking).
iNPUT jOUTPUT PKOCESSOR liOfij FUNUAMENTAlS
This section contains general information, programming con-
cepts, and definition of terms pertaining to I/O operations
performed by Input/Output Processors (i. e., MIOP and
RMP systems). The large variety of I/O devices which may
be used with these lOPs precludes a detailed or exhaustive
description of features which are unique to each device.
Likewise, a general reference "Refer to an appropriate
Xerox peripheral reference manual" is made rather than
citing specific manuals.
Within this manual, the following terminology is used to
differentiate the hierarchy of control during an I/o opera-
tion: The BP executes instructions, the lOPs execute com-
mands, and the device controller/device execute orders.
COMMAND LIST
Each I/O operation performed by an lOP must be defined
by a command list. The characteristics and requirements of
a command list are as follows:
1. It is normally created by a BP-executed program
prior to the time that the defined I/o operation is
initiated. It must reside in main memory when the I/o
operation is initiated and subsequently executed.
2. Depending upon various programming considerations,
the command list may be contained within one or more
areas of memory and each area may be comprised of
one or more I/O command doublewords (IOCDs).
3.
Command list continuity between 10CDs relating to the
same logical record or to the same logical file may be
specified (see "Data Chain Flag" and "Command Chain
Flag
ll
under II Operationa
I
10CDs"). Command list
continuity between portions of a command list located
in different areas of main memory may be accomplished
by including a control 10CD within the command list
(see "Transfer in Channel II under "Control 10CDs").
4.
Each 10CD is comprised of two words in contiguous
memory word locations. The first word must be stored
in an even memory word location and the second word
must be stored in the next consecutive (odd) memory
word location. Each IOCD is either an operational
IOCD or a control IOCD and contains coded parameters
to define either a complete I/Ooperation or an integral
portion of an I/Ooperation. (See "Operational IOCD"
and IIControl IOCD" for further detai Is. )
OPERATIONAL lOCO
An operational IOCD may contain up to five fields of
parameters, as required, to define either an entire I/o op-
eration or an integral portion of an I/o operation._ The
general format and description of parameters contained
within an operational 10CD are as follows:
ORDER
This 8-bit field (bit positions 0-7), if required, may be
coded to specify either an input or an output order that is
executed by the device controller/device. General coding
formats and functions of typical I/o orders are listed below:
Bit Position
o
1 2 3 4 5 6 7 Order Function
MMMMMM01
MMMMMM10
MMMMMM11
MMMMO
MMMM1
00
00
Write
Read
Control
Output operation
Input operation
Output control
information
Sense Input control information
Read Input data, in reverse
Backward sequence
Rotating Memory Processor (RMP)/Input/Output Processor (lOP) Fundamentals 143