IBM42M10SCYAA10
IBM42M10LCYAA20
1063Mb/s Gigabit Link Module
The timing intervals, Decode 1, 2, and 3, are provided by the OFC IC module (internal to the GLM card) and
are extremely accurate since they are driven by a 100ppm 53MHz clock. However, analog circuits on the
GLM such as the transmitter driver and receiver amplifier alter the exact timing behavior (see the Open Fibre
change the duration of the optical pulse emitted during the first Decode 1 timing interval. In addition, during all
three Decode timing intervals, the time it takes for the GLM to recognize (or detect) the presence or absence
of light must be included in the timing intervals. Three factors: the laser “ON-pulse” (T
ON
), the laser “OFF-
pulse” (T
OFF
), and the “response” time (T
resp
), are specified to ensure interoperability with other optical link
card manufacturers.
The Open Fibre Control Sequence During Enable Wrap timing diagram on page 7 shows the OFC sequence
during an Enable Wrap sequence. As mentioned earlier, if the link is active prior to turning on the Enable
Wrap signal, the OFC will respond to the Enable Wrap signal being brought low later by immediately initiating
the “on-off-on” handshake.
The Fault Sequence timing diagram on page 8 shows the timing for the Fault and Link Unusable signals with
Open Fibre Control.
Open Fibre Control Timing
OFC Timing: Disconnect
Photo-
GLM2
detector
Rx[00:19]
GLM2
Link
OFC Timing: Reconnect
Fiber Path Reconnected
OFC LD
T
Dcd1
T
Dcd2
T
LD
(off)
T
Dcd3
Fiber Path Disconnected
<650
µ
s
<170
µ
s
10.1s
T
ON
T
ON
GLM2
(electrical)*
Laser
GLM2
(optical)
T
LD
(on)
On-Pulse
GLM2
Unusable
Laser
GLM2
Photo-
detector
GLM1
Rx[00:19]
GLM1
Link
Unusable
GLM1
Laser
GLM1
Laser
GLM1
(optical)
t
fiber
+ T
resp
* This signal is internal to the card.
<650
µ
s
<170
µ
s
10.1s
T
ON
T
ON
Page 6 of 30
glm1063.02.fm.02
Feb. 15, 2000
IBM [ IBM ]
