APPLICATION NOTE 4638

DS1874 Quick Reference Guide

By: Hrishikesh Shinde

Abstract: This reference guide provides an alternate view of the register map for the DS1874 SFP+ controller with digital LDD interface. The register information is convenient when programming the device.

Introduction

The DS1874 SFP+ controller with digital LDD interface allows programming of various options required to configure the alarms, warnings, lookup tables (LUTs), etc. This programmability necessitates a large register memory map. This application note provides an alternate view of the register map, which is convenient during programming.

Memory Map of the DS1874

The DS1874 features nine separate memory tables that are internally organized into eight-byte rows.

The Lower memory is addressed from 00h to 7Fh and contains alarm and warning thresholds, flags, masks, several control registers, password entry area (PWE), and the Table Select byte.

Table 01h primarily contains user EEPROM (with PW1 level access) as well as alarm and warning-enable bytes.

Table 02h is a multifunction space that contains configuration registers, scaling and offset values, passwords, interrupt registers, and miscellaneous control bytes.

Table 04h contains a temperature-indexed LUT for controlling the modulation voltage. The modulation LUT can be programmed in 2°C increments over the -40°C to +102°C range.

Table 05h is empty by default. It can be configured to contain the alarm and warning-enable bytes from Table 01h, Registers F8h-FFh with the MASK bit enabled (Table 02h, Register 89h). In this case Table 01h will be empty.

Table 06h contains a temperature-indexed LUT that allows the APC set point to change as a function of temperature to compensate for Tracking Error (TE). The APC LUT has 36 entries that determine the APC setting in 4°C windows between -40°C and +100°C.

Table 07h contains a temperature-indexed LUT for control of DAC1. The LUT has 36 entries that determine the DAC setting in 4°C windows between -40°C and +100°C.

Table 08h contains a temperature-indexed LUT for control of DAC2. The LUT has 36 entries that determine the DAC setting in 4°C windows between -40°C and +100°C.

Auxiliary memory (device A0h) contains 256 bytes of EE memory accessible from address 00h to FFh. It is selected with the device address of A0h.

Refer to the tables below for a more complete detail of each byte's function, as well as for read/write permissions for each Byte.

Shadowed EEPROM

Many nonvolatile memory locations (listed within the Register reference section below) are actually shadowed EEPROM and are controlled by the SEEB bit in Table 02h, Register 80h.

The DS1874 incorporates shadowed EEPROM memory locations for key memory addresses that can be written many times. By default the shadowed EEPROM bit, SEEB, is not set and these locations act as ordinary EEPROM. By setting SEEB, these locations function like SRAM cells. This allows an infinite number of write cycles without concern of wearing out the EEPROM, and it eliminates the requirement for the EEPROM write time. Because changes made with SEEB enabled do not affect the EEPROM, these changes are not retained through power cycles. The power-on value is the last value written with SEEB disabled. This function can be used to limit the number of EEPROM writes during calibration, or to change the monitor thresholds periodically during normal operation. This monitoring helps to reduce the number of times that EEPROM is written. The memory map description indicates which locations are shadowed EEPROM.

DS1874 Memory Map

Figure 1. DS1874 memory map.

Register Reference

The following tables provide an easy reference to the Lower memory and Tables 01h and 02h. For a description of the functionality of each bit, please refer to the corresponding register in the data sheet. Tables 04h through 08h are LUTs that do not require a separate reference and, hence, are not included here. Please refer to the data sheet for detailed information about these tables.

Note: RSVD is used as an acronym for reserved.

Lower Memory
REGISTER NAME REGISTER ADDR (h) bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
TEMP ALARM HI
TEMP WARN HI
00h, 04h S 26 25 24 23 22 21 20
01h, 05h 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
TEMP ALARM LO
TEMP WARN LO
02h, 06h S 26 25 24 23 22 21 20
03h, 07h 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
VCC ALARM HI
VCC WARN HI
MON1-4 ALARM HI
MON1-4 WARN HI
08, 0C, 10, 14, 18, 1C, 20, 24, 28, 2Ch 215 214 213 212 211 210 29 28
09, 0D, 11, 15, 19, 1D, 21, 25, 29, 2Dh 27 26 25 24 23 22 21 20
VCC ALARM LO
VCC WARN LO
MON1-4 ALARM LO
MON1-4 WARN LO
0A, 0E, 12, 16, 1A, 1E, 22, 26, 2A, 2Eh 215 214 213 212 211 210 29 28
0B, 0F, 13, 17, 1B, 1F, 23, 27, 2B, 2Fh 27 26 25 24 23 22 21 20
PW2 EE 30h-5Fh EE EE EE EE EE EE EE EE
TEMP VALUE 60h S 26 25 24 23 22 21 20
61h 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
VCC VALUE
MON1-4 VALUE
62, 64, 66, 68, 6Ah 215 214 213 212 211 210 29 28
63, 65, 67, 69, 6Bh 27 26 25 24 23 22 21 20
RESERVED 6C, 6Dh 0 0 0 0 0 0 0 0
STATUS 6Eh TXDS TXDC IN1S RSELS RSELC TXF RXL RDYB
UPDATE 6Fh TEMP RDY VCC RDY MON1 RDY MON2 RDY MON3 RDY MON4 RDY RESERVED RSSIR
ALARM3 70h TEMP HI TEMP LO VCC HI VCC LO MON1 HI MON1 LO MON2 HI MON2 LO
ALARM2 71h MON3 HI MON3 LO MON4 HI MON4 LO RSVD RSVD RSVD TXFINT
ALARM1 72h RSVD RSVD RSVD RSVD HBAL RSVD TXP HI TXP LO
ALARM0 73h LOS HI LOS LO RSVD RSVD BIAS MAX RSVD RSVD RSVD
WARN3 74h TEMP HI TEMP LO VCC HI VCC LO MON1 HI MON1 LO MON2 HI MON2 LO
WARN2 75h MON3 HI MON3 LO MON4 HI MON4 LO RSVD RSVD RSVD RSVD
RESERVED 76h-7Ah RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
PASSWORD ENTRY 7Bh 231 230 229 228 227 226 225 224
7Ch 223 222 221 220 219 218 217 216
7Dh 215 214 213 212 211 210 29 28
7Eh 27 26 25 24 23 22 21 20
TABLE SELECT 7Fh 27 26 25 24 23 22 21 20

Table 01h
REGISTER NAME ADDR (h) bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
PW1 EEPROM 80h-BFh EE EE EE EE EE EE EE EE
PW2 EEPROM C0h-F7h EE EE EE EE EE EE EE EE
ALARM3 F8h TEMP HI TEMP LO VCC HI VCC LO MON1 HI MON1 LO MON2 HI MON2 LO
ALARM2 F9h MON3 HI MON3 LO MON4 HI MON4 LO RSVD RSVD RSVD RSVD
ALARM1 FAH RSVD RSVD RSVD RSVD HBAL RSVD TXP HI TXP LO
ALARM0 FBH LOS HI LOS LO RSVD RSVD BIAS MAX RSVD RSVD RSVD
WARN3 FCh TEMP HI TEMP LO VCC HI VCC LO MON1 HI MON1 LO MON2 HI MON2 LO
WARN2 FDh MON3 HI MON3 LO MON4 HI MON4 LO RSVD RSVD RSVD RSVD
RESERVED FEh-FFh RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD

Table 02h
REGISTER NAME ADDR (h) bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
MODE 80h SEEB RSVD DAC1 EN DAC2 EN AEN MOD EN APC EN BIAS EN
TINDEX 81h 27 26 25 24 23 22 21 20
MODULATION REGISTER 82h 0 0 0 0 0 0 0 28
83h 27 26 25 24 23 22 21 20
DAC1 VALUE 84h 0 0 0 0 0 0 0 28
85h 27 26 25 24 23 22 21 20
DAC2 VALUE 86h 0 0 0 0 0 0 0 28
87h 27 26 25 24 23 22 21 20
SAMPLE RATE 88h SEE SEE SEE SEE SEE APC_SR2 APC_SR1 APC_SR0
CNFGA 89h LOSC RSVD INV LOS ASEL MASK INVRSOUT RSVD RSVD
CNFGB 8Ah IN1C INVOUT1 RSVD RSVD RSVD ALATCH QTLATCH WLATCH
CNFGC 8Bh RSVD RSVD TXDM34 TXDFG TXDFLT TXDIO RSSI_FC RSSI_FF
DEVICE ADDR 8Ch 27 26 25 24 23 22 21 20
RESERVED 8Dh RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
RIGHT SHIFT1 8Eh RSVD MON12 MON11 MON10 RSVD MON22 MON21 MON20
RIGHT SHIFT0 8Fh RSVD MON32 MON31 MON30 RSVD MON42 MON41 MON40
RESERVED 90h-91h RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
VCC SCALE
MON1-2 SCALE
MON3 F SCALE
MON4 SCALE
MON3 C SCALE
92, 94, 96, 98, 9A, 9Ch 215 214 213 212 211 210 29 28
93, 95, 97, 99, 9B, 9Dh 27 26 25 24 23 22 21 20
RESERVED 9Eh-A1h RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
VCC OFFSET
MON1-2 OFFSET
MON3 F OFFSET
MON4 OFFSET
MON3 C OFFSET
A2, A4, A6, A8, AA, ACh S S 215 214 213 212 211 210
A3, A5, A7, A9, AB, ADh 29 28 27 26 25 24 23 22
INTERNAL TEMP OFFSET AEh S 28 27 26 25 24 23 22
AFh 21 20 2-1 2-2 2-3 2-4 2-5 2-6
PW1 B0h 231 230 229 228 227 226 225 224
B1h 223 222 221 220 219 218 217 216
B2h 215 214 213 212 211 210 29 28
B3h 27 26 25 24 23 22 21 20
PW2 B4h 231 230 229 228 227 226 225 224
B5h 223 222 221 220 219 218 217 216
B6h 215 214 213 212 211 210 29 28
B7h 27 26 25 24 23 22 21 20
LOS RANGING B8h RSVD HLOS2 HLOS1 HLOS0 RSVD LLOS2 LLOS1 LLOS0
COMP RANGING B9h RSVD BIAS2 BIAS1 BIAS0 RSVD APC2 APC1 APC0
RESERVED BAh RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
ISTEP BBh 28 27 26 25 24 23 22 21
HTXP BCh 27 26 25 24 23 22 21 20
LTXP BDh 27 26 25 24 23 22 21 20
HLOS BEh 27 26 25 24 23 22 21 20
LLOS BFh 27 26 25 24 23 22 21 20
PW_ENA C0h RWTBL78 RWTBL1C RWTBL2 RWTBL1A RWTBL1B WLOWER WAUXA WAUXB
PW_ENB C1h RWTBL46 RTBL1C RTBL2 RTBL1A RTBL1B WPW1 WAUXAU WAUXBU
MODTI C2h 27 26 25 24 23 22 21 20
DAC1TI C3h 27 26 25 24 23 22 21 20
DAC2TI C4h 27 26 25 24 23 22 21 20
RESERVED C5h RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
LUTTC C6h MODTC DAC1TC DAC2TC RSVD RSVD RSVD RSVD RSVD
TBLSELPON C7h 27 26 25 24 23 22 21 20
MAN BIAS C8h 0 0 0 0 0 0 0 28
C9h 27 26 25 24 23 22 21 20
MAN CNTL CAh RSVD RSVD RSVD RSVD RSVD RSVD RSVD MAN_CLK
BIAS REGISTER CBh RSVD RSVD RSVD RSVD RSVD RSVD RSVD 28
CCh 27 26 25 24 23 22 21 20
APC DAC CDh 27 26 25 24 23 22 21 20
DEVICE ID CEh 0 1 1 1 0 1 0 0
DEVICE VER CFh
DEVICE VERSION
HBATH D0h-D7h 27 26 25 24 23 22 21 20
EMPTY D8h-E7h
EMPTY
RXCNTRL1 E8h 27 26 25 24 23 22 21 20
RXCNTRL2 E9h 27 26 25 24 23 22 21 20
SETCML EAh 27 26 25 24 23 22 21 20
SETLOS EBh 27 26 25 24 23 22 21 20
TXCTRL ECh 27 26 25 24 23 22 21 20
IMODMAX EDh 27 26 25 24 23 22 21 20
IBIASMAX EEh 27 26 25 24 23 22 21 20
SETPWCTRL EFh 27 26 25 24 23 22 21 20
SETTXDE F0h 27 26 25 24 23 22 21 20
RESERVED F1h-F7h RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
3WCTRL F8h RSVD RSVD RSVD RSVD RSVD RSVD 3WRW 3WDIS
ADDRESS F9h 27 26 25 24 23 22 21 20
WRITE FAh 27 26 25 24 23 22 21 20
READ FBh 27 26 25 24 23 22 21 20
TXSTAT1 FCh 27 26 25 24 23 22 21 20
TXSTAT2 FDh 27 26 25 24 23 22 21 20
RESERVED FEh-FFh RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD


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APP 4638:
APPLICATION NOTE 4638,AN4638, AN 4638, APP4638, Appnote4638, Appnote 4638