4

64 x 36 x 2

COMMERCIALTEMPERATURERANGE

PIN DESCRIPTION (CONTINUED)

Symbol

Name

I/O

Description

MBF2

Mail2 Register Flag

O

MBF2 is set LOW by a LOW-to-HIGH transition of CLKB that writes data to the mail2 register.

Writes to the mail2 register are inhibited while MBF2 is set LOW. MBF2 is set HIGH by a LOW-to-

HIGH transition of CLKA when a port A read is selected and MBA is HIGH. MBF2 is set HIGH

when the device is reset.

ODD/

Odd/Even Parity

I

Odd parity is checked on each port when ODD/EVEN is HIGH, and even parity is checked when

EVEN

Select

ODD/EVEN is LOW. ODD/EVEN also selects the type of parity generated for each port if parity

generation is enabled for a read operation.

PEFA

Port A Parity Error

O

When any byte applied to terminals A0-A35 fails parity, PEFA is LOW. Bytes are organized as

Flag

(Port A)

A0-A8, A9-A17, A18-A26, and A27-A35, with the most significant bit of each byte serving as the

parity bit. The type of parity checked is determined by the state of the ODD/EVEN input. The

parity trees used to check the A0-A35 inputs are shared by the mail2 register to generate parity if

parity generation is selected by PGA. Therefore, if a mail2 read with parity generation is setup by

having W/RA LOW, MBA HIGH, and PGA HIGH, the PEFA flag is forced HIGH regardless of the

A0-A35 inputs.

PEFB

Port B Parity Error

O

When any byte applied to terminals B0-B35 fails parity, PEFB is LOW. Bytes are organized as

Flag

(Port B)

B0-B8, B9-B17, B18-B26, B27-B35 with the most significant bit of each byte serving as the parity

bit. The type of parity checked is determined by the state of the ODD/EVEN input. The parity trees

used to check the B0-B35 inputs are shared by the mail1 register to generate parity if parity

generation is selected by PGB. Therefore, if a mail1 read with parity generation is setup by having

W/RB LOW, MBB HIGH, and PGB HIGH, the PEFB flag is forced HIGH regardless of the state of

the B0-B35 inputs.

PGA

Port A Parity

I

Parity is generated for data reads from port A when PGA is HIGH. The type of parity generated is

Generation

selected by the state of the ODD/EVEN input. Bytes are organized as A0-A8, A9-A17, A18-A26,

and A27-A35. The generated parity bits are output in the most significant bit of each byte.

PGB

Port B Parity

I

Parity is generated for data reads from port B when PGB is HIGH. The type of parity generated is

Generation

selected by the state of the ODD/EVEN input. Bytes are organized as B0-B8, B9-B17, B18-B26,

and B27-B35. The generated parity bits are output in the most significant bit of each byte.

RST

Reset

I

To reset the device, four LOW-to-HIGH transitions of CLKA and four LOW-to-HIGH transitions of

CLKB must occur while RST is LOW. This sets the AFA, AFB, MBF1, and MBF2 flags HIGH and

the EFA, EFB, AEA, AEB, FFA, and FFB flags LOW. The LOW-to-HIGH transition of RST latches

the status of the FS1 and FS0 inputs to select Almost-Full and Almost-Empty flag offset.

W/RA

Port A Write/Read

I

A HIGH selects a write operation and a LOW selects a read operation on port A for a LOW-to-

Select

HIGH transition of CLKA. The A0-A35 outputs are in the high-impedance state when W/RA is

HIGH.

W/RB

Port B Write/Read

I

A HIGH selects a write operation and a LOW selects a read operation on port B for a LOW-to-

Select

HIGH transition of CLKB. The B0-B35 outputs are in the high-impedance state when W/RB is

HIGH.