M67204H
Table 1.
Reset and Retransmit
Single Device Configuration/Width Expansion Mode
Inputs
Mode
Reset
Retransmit
Read/Write
Note:
RS
0
1
1
RT
X
0
1
XI
0
0
0
Internal Status
Read Pointer
Location Zero
Location Zero
Increment
Write Pointer
Location Zero
Unchanged
Increment
(1)
EF
0
X
X
Outputs
FF
1
X
X
HF
1
X
X
1. Pointer will increment if flag is high.
Table 2.
Reset and First Load Truth Table
Depth Expansion/Compound Expansion Mode
Inputs
Mode
Reset First Device
Reset All Other Devices
Read/Write
Note:
RS
0
0
1
RT
0
1
X
XI
Internal Status
Read Pointer
Location Zero
Location Zero
X
Write Pointer
Location Zero
Location Zero
X
EF
0
0
X
Outputs
FF
1
1
X
1. XI is connected to XO of previous device.
See Figure 4.
Depth Expansion (Daisy
Chain) Mode
The M67204H can be easily adapted for applications which require more than 4096
words. Figure 4 demonstrates Depth Expansion using three M67204H. Any depth can
be achieved by adding additional M67204H.
The M67204H operates in the Depth Expansion configuration if the following conditions
are met:
1. The first device must be designated by connecting the First Load (FL) control
input to ground.
2. All other devices must have FL in the high state.
3. The Expansion Out (XO) pin of each device must be connected to the Expansion In
(XI) pin of the next device. See Figure 4.
4. External logic is needed to generate a composite Full Flag (FF) and Empty Flag
(EF). This requires that all EF’s and all FFs be ORed (i.e. all must be set to generate the
correct composite FF or EF). See Figure 4.
5. The Retransmit (RT) function and Half-Full Flag (HF) are not available in the Depth
Expansion Mode.
Compound Expansion
Module
It is quite simple to apply the two expansion techniques described above together to cre-
ate large FIFO arrays (see Figure 5).
7
4141J–AERO–04/07
ATMEL [ ATMEL CORPORATION ]
