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DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
51
b. The input drivers of the bi-directional data bus are
enabled.
NOTE: In order to insure that the XRT7250 DS3/E3 Framer
device will interpret this signal as being a Write signal, the
C/P should keep the WR_RW input pin "Low".
B.3
After some settling time, the data, in the inter-
nal data bus, will stabilize and is ready to be
latched into the Framer Microprocessor Inter-
face block. The Microprocessor Interface block
will indicate that this data is ready to be latched
by asserting the RDY_DTCK (DTACK) output
signal. At this point, the C/P should latch the
data into the Framer by toggling the RD_DS
input pin "High".
For subsequent write operations, within this burst I/O
access, the C/P simply repeats steps B.1 through
2.2.2.2.2.2.3
Terminating the Burst I/O Access
The Burst I/O Access will be terminated upon the fall-
ing edge of the ALE_AS input signal. At this point the
Framer will cease to internally increment the latched
address value. Further, the C/P is now free to exe-
cute either a Programmed I/O access or to start an-
other Burst I/O Access with the XRT7250 DS3/E3
Framer.
2.3
ON-CHIP REGISTER ORGANIZATION
The Microprocessor Interface section, within the
Framer device allows the user to do the following.
Configure the Framer into a wide variety of operat-
ing modes.
Employ various features of the Framer device.
Perform status monitoring
Enable/Disable and service Interrupt Conditions
All of these things are accomplished by reading from
and writing to the many on-chip registers within the
Framer device.
Table 4 lists each of these registers
and their corresponding address locations within the
Framer Address space.
2.3.1
Framer Register Addressing
The array of on-chip registers consists of a variety of
register types. These registers are denoted in
R/O - Read Only Registers.
R/W - Read/Write Registers
RUR - Reset-upon-Read Registers
Additionally, some of these registers consists of both
R/O and R/W bit-fields. These registers are denoted
in
Table 4 as Combination of R/W and R/O.
The bit-format and definitions for each of these regis-
ters are presented in Section 3.3.2
FIGURE 36. BEHAVIOR OF THE MICROPROCESSOR INTERFACE SIGNALS, DURING SUBSEQUENT WRITE OPERATIONS
WITH THE
BURST I/O CYCLE (MOTOROLA-TYPE C/P)
ALE_AS
RD_DS
A[8:0]
CS
D[15:0]
RDY_DTCK
Data Written at Offset =0x01
WR_RW
Data Written at Offset =0x02
Address of “Initial” Target Register (Offset = 0x00)