Agilent Technologies HDMP-3001 - Manual (Page 19)

19
3.4.2 LAPS Mode
In LAPS mode the FCS is calcu-
lated LSB first and the FCS sum is
transmitted in reversed bit order
within each byte. See Figure 6 and
Figure 7.
3.5 Performance Monitoring
For performance monitoring pur-
poses, the HDMP-3001 contains a
number of delta bits, event bits
and error counters.
Delta bits are set by the HDMP-
3001 when a monitored parameter
changes state. The delta bit then
stays high until the controller
TX_DATA[7]
TX_DATA[6]
TX_DATA[5]
TX_DATA[4]
TX_DATA[3]
TX_DATA[2]
TX_DATA[1]
TX_DATA[0] 7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
0
1
2
3
X
7
S
C
R
L
A
P
S
M
I
I
I
/
F
X
4
3
S
C
R
C
R
C
G
E
N
7 6 5 4 3 2 1 0
F L
[7] [0]
7 6 5 4 3 2 1 0
F L
0 1 2 3 4 5 6 7
F L
LSN
F
4
5
6
7
MSN
L
PINS
PINS
TXD0
TXD1
TXD2
TXD3
F = FIRST
L = LAST
TX_DATA[7]
TX_DATA[6]
TX_DATA[5]
TX_DATA[4]
TX_DATA[3]
TX_DATA[2]
TX_DATA[1]
TX_DATA[0] 7
6
5
4
3
2
1
0
X
7
S
C
R
X
4
3
S
C
R
C
R
C
G
E
N
7 6 5 4 3 2 1 0
F L
[7] [0]
PINS
7 6 5 4 3 2 1 0
F
X 24 X 31
7 6 5 4 3 2 1 0
X 16 X 23
7 6 5 4 3 2 1 0
X 8 X 15
7 6 5 4 3 2 1 0
L
X 0 X 7
Figure 6. LAPS Payload Bit Order
Figure 7. LAPS FCS Bit Order
clears the bit. If a clear occurs si-
multaneously with a parameter
state change, the delta bit remains
set. Delta bits are indicated by a
_D suffix.
When LATCH_CNT in register
0x001 is written from a 0 to a 1, it
produces a pulse on an internal
signal, LATCH_EVENT.
All the internal performance
monitoring counter blocks are
comprised of a running error
counter and a holding register
that presents stable results to the
controller. The counts in all of the
running counters are latched into
the hold registers and the running
counters are cleared when a pulse
occurs on LATCH_EVENT.
To prevent missing a count that
occurs when latching occurs, a
counter is set to one, rather than
zero, if the clear signal is simulta-
neous with an increment. After
being latched, the results are held
to be read by the microprocessor.
The running counters will stop at
their maximum value rather than
roll over to zero.