MAX1455 Datasheet, PDF (16/25 Pages) Maxim Integrated Products – Low-Cost Automotive Sensor Signal Conditioner

Low-Cost Automotive Sensor Signal
Conditioner
Table 10. CRIL Command Codes
CRIL[3:0]
NAME
DESCRIPTION
0000
LdICR
Load Internal Calibration register at address given in ICRA with data from DHR[15:0].
0001
0010
0011
EEPW
ERASE
RdICR
EEPROM write of 8 data bits from DHR[7:0] to address location pointed by IEEA [9:0].
Erase all of EEPROM (all bytes equal FFhex).
Read Internal Calibration register as pointed to by ICRA and load data into DHR[15:0].
0100
0101
0110
0111
1000 to
1111
RdEEP
RdIRS
RdAlg
PageErase
Read internal EEPROM location and load data into DHR[7:0] pointed by IEEA [9:0].
Read Interface register set pointer IRSP[3:0]. See Table 11.
Output the multiplexed analog signal onto OUT. The analog location is specified in ALOC[3:0]
(Table 13) and the duration (in byte times) that the signal is asserted onto the pin is specified in
ATIM[3:0] (Table 14).
Erases the page of the EEPROM as pointed by IEEA[9:6]. There are 64 bytes per page and thus 12
pages in the EEPROM.
Reserved Reserved.
5) Send the reinitialize command, followed by the ini-
tialize (baud rate learning) command.
The frequency of the internal oscillator can be checked
at any time by reading the value of BITCLK[7:0]. This 8-
bit number represents the number of internal oscillator
cycles corresponding to 1 cycle (1 bit time) of the com-
munications baud rate.
Erasing and Writing to the EEPROM
The internal EEPROM must be erased (bytes set to
FFhex) prior to programming the desired contents. The
MAX1455 is supplied in a nominally erased state
except byte 161hex and byte 16Bhex. The 3MSBs of
byte 161hex contain the internal oscillator calibration
setting. Byte 16Bhex is set to 00hex to allow serial com-
munication regardless of the UNLOCK status.
When erasing the EEPROM, first save the 3MSBs of
byte 161hex. Following erasure, these 3 bits must be
rewritten, together with the Secure-Lock byte value of
00hex. Failure to do this may cause the part to stop
communicating. Do not remove power from the
device before rewriting these values.
The internal EEPROM can be entirely erased with the
ERASE command or partially erased with the
PageErase command (Table 10). It is necessary to wait
7.1ms after issuing an erase or PageErase command.
Any attempt to communicate with the part or to interrupt
power before 7.1ms have elapsed may produce inde-
terminate states within the EEPROM.
To erase a page in EEPROM (PageErase command):
First load the required page number (Table 1) into the
IRS location IEEA[3:0]. Then send a CRIL PageErase
command (79hex).
To write a byte to EEPROM: Load IRS locations
IEEA[9:8], IEEA[7:4], and IEEA[3:0] with the byte
address (Address[9:0]). Load IRS locations DHR[7:4]
and DHR[3:0] with the 8 data bits to be written
(Data[7:0]). Send the EEPROM WRITE command to
CRIL (19hex).
To read a byte from EEPROM:
1) Load IRS locations IEEA[9:8], IEEA[7:4], and
IEEA[3:0] with the byte address (Address[9:0]).
2) Send a READ EEPROM command to the CRIL reg-
ister (49hex); this loads the required EEPROM byte
into DHR[7:0].
3) Load IRS location IRSP[3:0] with 00hex (return
DHR[7:0]).
4) Send the READ IRSP command to the CRIL register
(59hex).
Multiplexed Analog Output
The MAX1455 provides the facility to output analog sig-
nals while in digital mode through the read analog
(RdAlg) command. One byte time after receiving the
RdAlg command, the internal analog signal determined
by the ALOC[3:0] register (Table 13) is multiplexed to
the MAX1455 OUT. The signal remains connected to
OUT for the duration set by the ATIM[3:0] register. The
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