ks8701 Samsung Semiconductor, Inc., ks8701 Datasheet - Page 17

• Manufacturer Part Number: ks8701
• Description: Flextm Roaming Decoder Ii
• Manufacturer: Samsung Semiconductor, Inc.

Host-to-Decoder Packet Descriptions
packets should be sent MSB first (bit 7 of byte 3 = bit 31 of the packet = MSB).
CHECKSUM PACKET
KS8701 exclusive-or’s the 24 data bits of every packet it receives (except the Checksum Packet and the special
packet ID’ s 1C through 1F hexadecimal) with an internal checksum register. Upon reset and whenever the host
writes a packet to the KS8701, the KS8701 is disabled from sending any information to the host processor until
the host processor sends a Checksum Packet with the proper checksum value (CV) to the KS8701. When the
KS8701 is disabled in this way, it prompts the host to read the Part ID Packet. Note that all other operation
continues normally when the KS8701 is “disabled”. Disabled only implies that data cannot be read, all other
internal operations continue to function.
defined in the Part ID Packet. See “Part ID Packet” on page 53 for a description of the Part ID. Every time a
packet other than the Checksum Packet and the special packets 1C through 1F is sent to the KS8701, the value
sent in the 24 information bits is exclusive-or’ed with the internal checksum register, the result is stored back to
the checksum register, and the KS8701 is disabled. If a Checksum Packet is sent and the CV bits match the bits
in the checksum register, the KS8701 is enabled. If a Checksum Packet is sent when the KS8701 is already
enabled, the packet is ignored by the KS8701 in which case a null packet having the ID and data bits set to 0 is
suggested. If a packet other than the Checksum Packet is sent when the KS8701 is enabled, the KS8701 will be
disabled until a Checksum Packet is sent with the correct CV bits.
sent so the KS8701 will not be disabled. The data in the Checksum Packet could be a null packet (32 bit stream of
all zeros) since a Checksum Packet will not disable the KS8701. When the host re-configures the KS8701, the
KS8701 will be disabled from sending any packets other than the Part ID Packet until the KS8701 is enabled with
a Checksum Packet having the proper data. The ID of the Checksum Packet is 0.
Table 3: Checksum Packet Bit Assignments
16
The following sections describe the packets of information sent from the host to the KS8701. In all cases the
The Checksum Packet is used to insure proper communication between the host and the KS8701. The
When the KS8701 is reset, it is disabled and the internal checksum register is initialized to the 24 bit part ID
When the host reads a packet out of the KS8701 but has no data to send, the Checksum Packet should be
CV:
Byte 3
Byte 2
Byte 1
Byte 0
Checksum Value.
HOST-TO-DECODER PACKET DESCRIPTIONS
Bit 7
CV
CV
CV
0
23
15
7
Bit 6
CV
CV
CV
0
22
14
6
Bit 5
CV
CV
FLEX
CV
0
21
13
5
TM
Roaming Decoder II
Bit 4
CV
CV
CV
0
20
12
4
Bit 3
CV
CV
CV
0
19
11
3
Bit 2
CV
CV
CV
0.
18
10
2
Bit 1
CV
CV
CV
0
17
9
1
Bit 0
CV
CV
CV
KS8701
0
16
8
0