Operational Characteristics
LANCAM B Family
removing the device from the daisy chain. With the Match
Flag disabled, /MF=/MI and operations directed to
Highest-Priority Match locations are ignored. Normal
operation of the device is with the /MF enabled. The
Match Flag Enable field has no effect on the /MA or /MM
output pins or Status Register bits. These bits always
reflect the true state of the device.
Segment Control Register (SC)
The Segment Control register, as shown in Segment
Control Register Bits on page 23, is accessed using a TCO
SC instruction. On read cycles, D15, D10, D5, and D2
always read back as 0s. Either the Foreground or
Background Segment Control register is active, depending
on which register set is selected, and only the active
Segment Control register is written to or read from.
If the Full Flag is disabled through bit 12 and bit 11, the
device behaves as if it is full and ignores instructions to
Next Free address. Also, writes to the Page Address
register are disabled. All other instructions operate
normally. Additionally, with the /FF disabled, /FF=/FI.
Normal operation of the device is with the /FF enabled.
The Full Flag Enable field has no effect on the /FL Status
Register bit. This bit always reflects the true state of the
device.
The Segment Control register contains dual independent
incrementing counters with limits, one for data reads and
one for data writes. These counters control which 16-bit
segment of the 64-bit internal resource is accessed during
a particular data cycle on the 16-bit data bus. The actual
destination for data writes and source for data reads (called
the persistent destination and source) are set independently
with SPD and SPS instructions, respectively.
The IEEE Translation control at bit 10 and bit 9 can be
used to enable the translation hardware for writes to 64-bit
resources in the device. When translation is enabled, the
bits are reordered as shown in Figure 6.
Each of the two counters consists of a start limit, an end
limit, and the current count value that points to the
segment to be accessed on the next data cycle. The current
count value can be set to any segment, even if it is outside
the range set by the start and end limits. The counters
count up from the current count value to the end limit and
then jump back to the start limit. If the current count is
greater than the end limit, the current count value
increments to three, rolls over to zero, continues
incrementing until the end limit is reached, and then jumps
back to the start limit.
DQ15
DQ8 DQ7
DQ0
If a sequence of data writes or reads is interrupted, the
Segment Control register can be reset to its initial start
limit values by using an RSC instruction. After the
LANCAM is reset, both Source and Destination counters
are set to count from Segment 0 to Segment 3 with an
initial value of 0.
DQ15
DQ8 DQ7
DQ0
Figure 6: IEEE 802.3/802.5 Format Mapping
Control Register bits 8–6 control the CAM/RAM
partitioning. The CAM portion of each word may be sized
from a full 64 bits down to 16 bits in 16-bit increments.
The RAM portion can be at either end of the 64-bit word.
Compare masks may be selected by bit 5 and bit 4. Mask
Register 1, Mask Register 2, or neither may be selected to
mask compare operations. The address register behavior is
controlled by bit 3 and bit 2, and may be set to increment,
decrement, or neither after a memory access. Bit 1 and bit
0 set the operating mode: Standard or Enhanced as shown
in Table 4 on page 12. The device resets to the Standard
mode, and follows the operating responses of the original
MU9C1480 in Table 4. When operating in Enhanced
mode, it is not necessary to unlock the daisy chain with a
NOP instruction before command or data writes after a
non-matching compare, as required in Standard mode.
Rev. 5.1
9
MUSIC [ MUSIC SEMICONDUCTORS ]
