25
IDT72V51433/72V51443/72V51453 3.3V, MULTI-QUEUE FLOW-CONTROL DEVICES
(16 QUEUES) 18 BIT WIDE CONFIGURATION 589,824, 1,179,648 and 2,359,296 bits
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
queues were setup, so when sector 2 is selected the unused outputs PAE[2:7]
will be don't care states.
Note, that if a read or write operation is occurring to a specific queue, say
queue ‘x’ on the same cycle as a sector switch which will include the queue ‘x’,
then there may be an extra RCLK cycle delay before that queues status is
correctly shown on the respective output of the PAEn bus.
Sectors can be selected on consecutive clock cycles, that is the sector on the
PAEn bus can change every RCLK cycle. Also, data can be read out of a queue
on the same RCLK rising edge that a sector is being selected, the only restriction
being that a read queue selection and PAEn sector selection cannot be made
on the same RCLK cycle.
If 8 or less queues are setup then queues, Queue[0:7] have their PAE status
output on PAE[0:7] constantly.
When the multi-queue devices are connected in expansion of more than one
device the PAEn busses of all devices are connected together, when switching
between sectors of different devices the user must utilize the 3 most significant
bits of the RDADD address bus (as well as the 2 LSB’s). These 3 MSB’s
correspond to the device ID inputs, which are the static inputs, ID0, ID1 & ID2.
Please refer to Figure 22,
PAE
n - Direct Mode Sector Selection for timing
information. Also refer to Table 2, Read Address Bus, RDADD.
PAEn – POLLED BUS
If FM is HIGH at master reset then the PAEn bus operates in Polled (looped)
mode. In polled mode the PAEn bus automatically cycles through the 2 sectors
within the device regardless of how many queues have been setup in the part.
Every rising edge of the RCLK causes the next sector to be loaded on the PAEn
bus. The device configured as the master (MAST input tied HIGH), will take
control of the PAEn after MRS goes LOW. For the whole RCLK cycle that the
first sector is on PAEn the ESYNC (PAEn bus sync) output will be HIGH, for the
2nd sector, this ESYNC output will be LOW. This ESYNC output provides the
user with a mark with which they can synchronize to the PAEn bus, ESYNC is
always HIGH for the RCLK cycle that the first sector of a device is present on
the PAEn bus.
When devices are connected in expansion mode, only one device will be
set as the Master, MAST input tied HIGH, all other devices will have MAST tied
LOW. The master device is the first device to take control of the PAEn bus and
will place its first sector on the bus on the rising edge of RCLK after the MRS input
goes LOW. For the next 3 RCLK cycles the master device will maintain control
of the PAEn bus and cycle its sectors through it, all other devices hold their PAEn
outputs in High-Impedance. When the master device has cycled its sectors it
passes a token to the next device in the chain and that device assumes control
of the PAEn bus and then cycles its sectors and so on, the PAEn bus control
token being passed on from device to device. This token passing is done via
the EXO outputs and EXI inputs of the devices (“PAE Expansion Out” and “PAE
Expansion In”). The EXO output of the master device connects to the EXI of the
second device in the chain and the EXO of the second connects to the EXI of
the third and so on. The final device in a chain has its EXO connected to the EXI
of the first device, so that once the PAEn bus has cycled through all sectors of
all devices, control of the PAEn will pass to the master device again and so on.
The ESYNC of each respective device will operate independently and simply
indicate when that respective device has taken control of the bus and is placing
its first sector on to the PAEn bus.
When operating in single device mode the EXI input must be connected to
the EXO output of the same device. In single device mode a token is still required
to be passed into the device for accessing the PAEn bus.
Please refer to Figure 27,
PAE
n Bus – Polled Mode for timing information.
