ISSUE 4.2:November1998
MFM8126S-70/90/12
Read Mode
The MFM8126 has two control functions which must be satisfied in order to obtain data at the outputs
CS is the power control and should be used for device selection
OE is the output control and should be used to gate data to the output pins if the device is selected.
Standby Mode
Two standby modes are available :
CMOS standby : CS held at Vcc +/- 0.5V
TTL standby : CS held at VIH
In the standby mode the outputs are in a high impedance state independent of the OE input. If the device is
deselected during erasure or programming the device will draw active current until the operation is completed.
OutputDisable
With the OE input at a logic high level (VIH), output from the device is disabled. This will cause the output pins
to be in a high impedance state.
Autoselect
The autoselect mode allows the reading out of a binary code from the device and will identify the device manu-
facturer and type. This mode is intended for use by programming equipment. This mode is functional over the full
military temperature range. The autoselect codes are as follows :
A16
A15
A14 A1 A0 CODE D7 D6 D5 D4 D3 D2 D1
D0
(HEX)
DIEManufacturercode
DIE device code
X
X
X
X
X
X
VIL VIL 01H
VIL VIH 20H
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
Sector protection
Sector Address VIH VIL 01H*
* Outputs 01H at protected sector address. Outputs 00H at unprotected sector address.
To activate this mode the programming equipment must force VID (11.5 to 12.5V) on address A9. Two identifier
bytes may then be sequenced from the device outputs by toggling A0 from VIL to VIH. All addresses are dont care
apart from A1 & A0. All identifiers for manufacturer and device will exhibit odd parity with D7 defined as the parity
bit.
The manufacturer and device codes may also be read via the command register, for instances when the
MFM8126 is erased or programmed in a system without access to high voltage on A9. All identifiers for
manufacturers and device will exhibit odd parity with the MSB(D7) defined as the parity bit. In order to read the
proper device codes when executing the Autoselect, A1 must be VIL.
Write
Device erasure and programming are accomplished via the command register. The contents of the register serve
as inputs to the internal state machine. The state machine outputs dictate the function of the device. The regis-
ter is a latch used to store the commands along with the address and data information required to execute the
command. The command register is written by bringing WE to VIL while CS is at VIL and
OE is at VIH.Addresses are latched on the falling edge of WE while data is latched on the rising edge.
12
MOSAIC [ MOSAIC ]
