COM90C66 Datasheet, PDF (17/76 Pages) SMSC Corporation – ARCNET Controller/Transceiver with AT Interface and On-Chip RAM

A13 = 1:
8K PROM SPACE
A13 = 1:
UPPER 8K PROM SPACE
A13 = 0:
A11 AND A12 Select one
of these 2K RAM segments.
A13 = O:
Lower 8K PROM SPACE
FIGURE 7 - 16K MEMORY SEGMENT
CHOSEN BY MS0-MS4
(Memory Mapped Mode)
FIGURE 8 - 16K PROM SEGMENT
CHOSEN BY MSO-MS4
(I/O Mapped, 16K X 8 Mode)
SHORT PACKET
FORMAT (256 OR 512 BYTE PAGE)
LONG PACKET
FORMAT (512 BYTE PAGE)
0
1
2
COUNT
SID
DID
COUNT = 256-N
NOT USED
DATA BYTE 1
DATA BYTE 2
0
1
2
3
COUNT
SID
DID
0
COUNT = 512-N
NOT USED
DATA BYTE 1
N = DATA PACKET LENGTH
SID = SOURCE ID
DID = DESTINATION ID
(DID = 0 FOR BROADCASTS)
DATA BYTE 2
DATA BYTE N-1
255
DATA BYTE N
511
NOT USED
DATA BYTE N-1
511
DATA BYTE N
FIGURE 9 – RAM BUFFER PACKET CONFIGURATION
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