谢谢yanxiao的提醒，我按照zwl以前发帖的思路又重新编了一段，调试已经正常。
1。读取变频器的频率。发送SOH+02+ENQ+J+ETX+D4
MAIN
NETWORK1

LDN T32
TON T96, +5

NETWORK2

LD T96
TON T32, +5

NETWORK3

LD SM0.0
MOVB 8, VB0
MOVB 16#01, VB1
MOVB 16#30, VB2
MOVB 16#32, VB3
MOVB 16#05, VB4
MOVB 16#6A, VB5
MOVB 16#03, VB6
MOVB 16#44, VB7
MOVB 16#34, VB8

NETWORK4

LD SM0.1
MOVB 9, SMB30
MOVB 2#110100, SMB87
MOVB 16#01, SMB88
MOVB 16#03, SMB89
MOVW +5, SMW92
MOVW +5, SMW90
MOVB 50, SMB94
ATCH INT_0, 9
ATCH INT_1, 23
ENI
R SM87.7, 1
R M0.0, 1

NETWORK5

LD T96
EU
XMT VB0, 0

NETWORK6

LD M0.0
EU
RCV VB100, 0

INT_0

LD SM0.0
S SM87.7, 1
S M0.0, 1
= Q0.0

INT_1

LD SM0.0
R M0.0, 1
R SM87.7, 1
= Q0.2
如有不妥之处请大家帮我指正。我对SMB87还不太清楚，做实验时是一个个调的。
2。我想再发送/读取电流值应该怎么做呀？是发送/读取完频率值，再发送/读取电流值吗？应怎样协调。谢谢