LM628 datasheet(13/24 Pages) NSC

13 / 24 page

Initialization Commands (Continued)

This command declares the current position as “home”, or

absolute position 0 (Zero). If DFH is executed during motion

it will not affect the stopping position of the on-going move

unless command STT is also executed.

Interrupt Control Commands

The following seven LM628 user commands are associated

with conditions which can be used to interrupt the host com-

puter. In order for any of the potential interrupt conditions to

actually interrupt the host via Pin 17, the corresponding bit in

the interrupt mask data associated with command MSKI

must have been set to logic high (the non-masked state).

The identity of all interrupts is made known to the host via

reading and parsing the status byte. Even if all interrupts are

masked off via command MSKI, the state of each condition

is still reflected in the status byte. This feature facilitates poll-

ing the LM628 for status information, as opposed to interrupt

driven operation.

SIP COMMAND: Set Index Position

Command Code:

03 Hex

Data Bytes:

None

Executable During Motion: Yes

After this command is executed, the absolute position which

corresponds to the occurrence of the next index pulse input

will be recorded in the index register, and bit 3 of the status

byte will be set to logic high. The position is recorded when

both encoder-phase inputs and the index pulse input are

logic low. This register can then be read by the user (see de-

scription for command RDIP) to facilitate aligning the defini-

tion of home position (see description of command DFH)

with an index pulse. The user can also arrange to have the

LM628 interrupt the host to signify that an index pulse has

occurred. See the descriptions for commands MSKI and

RSTI.

LPEI COMMAND: Load Position Error for Interrupt

Command Code:

1B Hex

Data Bytes:

Two

Data Range:

0000 to 7FFF Hex

Executable During Motion: Yes

An excessive position error (the output of the loop summing

junction) can indicate a serious system problem; e.g., a

stalled rotor. Instruction LPEI allows the user to input a

threshold for position error detection. Error detection occurs

when the absolute magnitude of the position error exceeds

the threshold, which results in bit 5 of the status byte being

set to logic high. If it is desired to also stop (turn off) the mo-

tor upon detecting excessive position error, see command

LPES, below. The first byte of threshold data written with

command LPEI is the more significant. The user can have

the LM628 interrupt the host to signify that an excessive po-

sition error has occurred. See the descriptions for com-

mands MSKI and RSTI.

LPES COMMAND: Load Position Error for Stopping

Command Code:

1A Hex

Data Bytes:

Two

Data Range:

0000 to 7FFF Hex

Executable During Motion: Yes

Instruction LPES is essentially the same as command LPEI

above, but adds the feature of turning off the motor upon de-

tecting excessive position error. The motor drive is not actu-

ally switched off, it is set to half-scale, the offset-binary code

for zero. As with command LPEI, bit 5 of the status byte is

also set to logic high. The first byte of threshold data written

with command LPES is the more significant. The user can

have the LM628 interrupt the host to signify that an exces-

sive position error has occurred. See the descriptions for

commands MSKI and RSTI.

SBPA COMMAND:

Command Code:

20 Hex

Data Bytes:

Four

Data Range:

C0000000 to 3FFFFFFF Hex

Executable During Motion: Yes

This command enables the user to set a breakpoint in terms

of absolute position. Bit 6 of the status byte is set to logic

high when the breakpoint position is reached. This condition

is useful for signaling trajectory and/or filter parameter up-

dates. The user can also arrange to have the LM628 inter-

rupt the host to signify that a breakpoint position has been

reached. See the descriptions for commands MSKI and

RSTI.

SBPR COMMAND:

Command Code:

21 Hex

Data Bytes:

Four

Data Range:

See Text

Executable During Motion: Yes

This command enables the user to set a breakpoint in terms

of relative position. As with command SBPA, bit 6 of the sta-

tus byte is set to logic high when the breakpoint position

(relative to the current commanded target position) is

reached. The relative breakpoint input value must be such

that when this value is added to the target position the result

remains within the absolute position range of the system

(C0000000 to 3FFFFFFF hex). This condition is useful for

signaling trajectory and/or filter parameter updates. The user

can also arrange to have the LM628 interrupt the host to sig-

nify that a breakpoint position has been reached. See the de-

scriptions for commands MSKI and RSTI.

MSKI COMMAND: MaSK Interrupts

Command Code:

1C Hex

Data Bytes:

Two

Data Range:

See Text

Executable During Motion: Yes

The MSKI command lets the user determine which potential

interrupt condition(s) will interrupt the host. Bits 1 through 6

of the status byte are indicators of the six conditions which

are candidates for host interrupt(s). When interrupted, the

host then reads the status byte to learn which condition(s)

occurred. Note that the MSKI command is immediately fol-

lowed by two data bytes. Bits 1 through 6 of the second (less

significant) byte written determine the masked/unmasked

status of each potential interrupt. Any zero(s) in this 6-bit

field will mask the corresponding interrupt(s); any one(s) en-

able the interrupt(s). Other bits comprising the two bytes

have no effect. The mask controls only the host interrupt pro-

cess; reading the status byte will still reflect the actual condi-

tions independent of the mask byte. See Table 3.

LM628 Scheda tecnica(PDF) 13 Page - National Semiconductor (TI)

LM628 Scheda tecnica(HTML) 13 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Scheda tecnica Scarica

Link URL