Service manual

EXTERNAL SERIAL CONTROL PROTOCOL
B-6
April 2001
Part No. 001-9800-203
Figure B-1 External Device Access To Subscriber Logic Controller
External DeviceSubscriber Unit
INFO_BUS_ACCESS_PERMITTED
( 1 every 10 seconds )
EVENT_POWER_ON_REQUEST
CMD_POWER_ON
DA = Registered Bus Address
[ RESPONSE_TYPE ]
ALLOWED
N
OT ALLOWED
The External Device may now
use Standard Operating Mode
Commands.
The External Device is not
allowed to access the Data Bus
at this time.
[ DA = 0xff ]
[ DA = 0x01 ]
[ Ext Dev Serial Number ]
[ Subscriber Model ]
[ POWER_ON_TYPE ]
[ Ext Dev Serial Number ]
ACK
[ DA = 0x01]
B.2.7 ERROR HANDLING
If any device on the control bus decodes a packet
with an invalid checksum, the packet must be ignored.
This protocol does not guarantee delivery of packets
except where stated. It only guarantees that detectable
corruption did not occur in the delivered packets.
B.2.8 MULTIPLE FRAME SUPPORT
This protocol does not support multiple
outstanding frames between the subscriber unit and
any one external device. When a frame is sent that
requires an ACK or NAK response, the source device
should not send another until the first frame is prop-
erly acknowledged. However, each external device
can have an outstanding ACK or NAK frame with the
subscriber unit. Broadcast frames can be sent between
directed frames in either direction.
B.3 UNREGISTERED MODE
B.3.1 INTRODUCTION
The “Unregistered” mode is the initial operating
mode entered upon power up reset. When this mode is
active, only a very limited set of messages are avail-
able. All external devices must negotiate with the
subscriber logic controller before entering another
mode.