PDP11 PeripheralsHbk 1972 - Trailing-Edge

ation repeated. Indicates that the program
has either selected a non-existent tape
unit or has attempted to select more than
one tape unit. Stops selected tape unit.
Disabled if MAINT bit (bit 13 in TCCM) is
set or if function is SAT (bits 03, 02, and
01 in TCCM cleared). Cleared when unit
selection s,witches set to valid positions
and selection repeated.
10 Block Missed (BLKM) Indicates a block was missed. The transfer
from read block number (RNUM) to read
data (RDATA) or write data (WDATA)
functions occurred too late. Also, indicates
switch from RDATA to WDATA was
too late. Cleared in the same manner as
EN Dl (bit 15).
9 Data Missed (DATM) Indicates data was missed. Request for
data transfer not honored in time during
RDATA, WDATA, WAll, or RAlL. Cleared
in the same manner as ENDl (bit 15).
8 Non-Existent Memory(NEX) Indicates non-existent memory. This occurs
when TC11 Controller is bus master
and does not receive a SSYN response within
20 Ils after asserting MSYN. Cleared
in the same manner as ENDl (bit 15).
7 Tape Is Up To Speed(UPS) Indicates that selected tape unit is up to
speed required for proper operation.
Cleared by INIT; cleared when UNIT SElECT
or REV bit is changed. Set when unit
is up to speed; set when MAINT bit (bit 13
in command register) is set.
6 Clock Simulates Timing (ClK)
5 Maint Mark Track (MMT)
4-2 Data Tracks (DT)
1-0 Extended Data (XD)
Used to simulate timing track. May be
loaded when MAINT bit is set. When CLK
is set, produces TPl: when cleared, produces
TPO.
Used to simulate the bit read from the
mark track. May be loaded when MAINT
bit is set. Cleared by INIT.
Used to simulate output of the read amplifer.
When MAINT bit is set. DTO loads into
RWB2 and reads as RWB5: DTl loads into
RWB1 and reads as RWB4; DT2 loads into
RWBO, reads as RWB3.
Extended data bit 17 or 16, which allow
reading and writing on areas of the tape
not accessible during 16-bit word transfers.
Cleared by INIT.
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