Data Reporting Commands (Continued)
Bit
Function
Position
Bit 3, the index-pulse acquired interrupt flag, is set to logic
one when an index pulse has occurred (if command SIP had
been executed) and indicates that the index position register
has been updated. The flag is functional independent of the
host interrupt mask status. Bit 3 is cleared by command
RSTI.
Bit
Bit
1
0
Command Error [Interrupt]
Acquire Next Index (SIP Executed)
Bit 15, the host interrupt flag, is set to logic one when the
host interrupt output (Pin 17) is logic one. Pin 17 is set to
logic one when any of the six host interrupt conditions occur
(if the corresponding interrupt has not been masked). Bit 15
(and Pin 17) are cleared via command RSTI.
Bit 2, the trajectory complete interrupt flag, is set to logic one
when the trajectory programmed by the LTRJ command and
initiated by the STT command has been completed. Be-
cause of overshoot or a limiting condition (such as com-
manding the velocity to be higher than the motor can
achieve), the motor may not yet be at the final commanded
position. This bit is the logical OR of bits 7 and 10 of the Sig-
nals Register, see command RDSIGS below. The flag func-
tions independently of the host interrupt mask status. Bit 2 is
cleared via command RSTI.
Bit 14, the acceleration-loaded flag, is set to logic one when
acceleration data is written to the LM628. Bit 14 is cleared by
the STT command.
Bit 13, the UDF-executed flag, is set to logic one when the
UDF command is executed. Because bit 13 is cleared at the
end of the sampling interval in which it has been set, this sig-
nal is very short-lived and probably not very profitable for
monitoring.
Bit 1, the command-error interrupt flag, is set to logic one
when the user attempts to read data when a write was ap-
propriate (or vice versa). The flag is functional independent
of the host interrupt mask status. Bit 1 is cleared via com-
mand RSTI.
Bit 12, the forward direction flag, is meaningful only when the
LM628 is in velocity mode. The bit is set to logic one to indi-
cate that the desired direction of motion is “forward”; zero in-
dicates “reverse” direction. Bit 12 is set and cleared via com-
mand LTRJ. The actual setting and clearing of bit 12 does
not occur until command STT is executed.
Bit 0, the busy flag, is frequently tested by the user (via the
host computer program) to determine the busy/ready status
prior to writing and reading any data. Such writes and reads
may be executed only when bit 0 is logic zero (not busy). Any
command or data writes when the busy bit is high will be ig-
nored. Any data reads when the busy bit is high will read the
current contents of the I/O port buffers, not the data ex-
pected by the host. Such reads or writes (with the busy bit
high) will not generate a command-error interrupt.
Bit 11, the velocity mode flag, is set to logic one to indicate
that the user has selected (via command LTRJ) velocity
mode. Bit 11 is cleared when position mode is selected (via
command LTRJ). The actual setting and clearing of bit 11
does not occur until command STT is executed.
Bit 10, the on-target flag, is set to logic one when the trajec-
tory generator has completed its functions for the last-issued
STT command. Bit 10 is cleared by the next STT command.
RDSIGS COMMAND: ReaD SIGnalS Register
Bit 9, the turn-off on-error flag, is set to logic one when com-
mand LPES is executed. Bit 9 is cleared by command LPEI.
Command Code:
Bytes Read:
0C Hex
Two
Bit 8, the 8-bit output flag, is set to logic one when the LM628
is reset, or when command PORT8 is executed. Bit 8 is
cleared by command PORT12.
Data Range:
See Text
Executable During Motion: Yes
Bits 0 through 7 replicate the status byte (see ), with the ex-
ception of bit 0. Bit 0, the acquire next index flag, is set to
logic one when command SIP is executed; it then remains
set until the next index pulse occurs.
The LM628 internal “signals” register may be read using this
command. The first byte read is the more significant. The
less significant byte of this register (with the exception of bit
0) duplicates the status byte. See Table 8.
RDIP COMMAND: ReaD Index Position
TABLE 8. Signals Register Bit Allocation
Command Code:
Bytes Read:
09 Hex
Four
Bit
Position
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Function
Data Range:
C0000000 to 3FFFFFFF Hex
Executable During Motion: Yes
Host Interrupt
This command reads the position recorded in the index reg-
ister. Reading the index register can be part of a system er-
ror checking scheme. Whenever the SIP command is ex-
ecuted, the new index position minus the old index position,
divided by the incremental encoder resolution (encoder lines
times four), should always be an integral number. The RDIP
command facilitates acquiring these data for host-based cal-
culations. The command can also be used to identify/verify
home or some other special position. The bytes are read in
most-to-least significant order.
Acceleration Loaded (But Not Updated)
UDF Executed (But Filter Not yet Updated)
Forward Direction
Velocity Mode
On Target
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
9
8
7
6
5
4
3
2
Turn Off upon Excessive Position Error
Eight-Bit Output Mode
Motor Off
Breakpoint Reached [Interrupt]
Excessive Position Error [Interrupt]
Wraparound Occurred [Interrupt]
Index Pulse Acquired [Interrupt]
Trajectory Complete [Interrupt]
RDDP COMMAND: ReaD Desired Position
Command Code:
Bytes Read:
08 Hex
Four
Data Range:
C0000000 to 3FFFFFFF Hex
Executable During Motion: Yes
17
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