Datasheet
AD9557 Data Sheet
Rev. B | Page 56 of 92
REGISTER MAP
Register addresses that are not listed in Table 35 are not used, and writing to those registers has no effect. The user should write the default
value to sections of registers marked reserved. R = read only. A = autoclear. E = excluded from EEPROM loading. L = live (I/O update not
required for register to take effect or for a read-only register to be updated).
Table 35. Register Map
Reg
Addr
(Hex) Opt Name D7 D6 D5 D4 D3 D2 D1 D0 Def
Serial Control Port Configuration and Part Identification
0x0000 L, E SPI control SDO enable
LSB first/
increment
address
Soft reset Reserved 00
0x0000 L I²C control Reserved Soft reset Reserved 00
0x0004
Readback
control
Reserved
Read buffer
register
00
0x0005 A, L I/O update Reserved I/O update 00
0x0006 L
User scratch
pad
User scratch pad[7:0] 00
0x0007 L User scratch pad[15:8] 00
0x000A R, L Silicon rev Silicon revision[7:0] 21
0x000B R, L Reserved Reserved 0D
0x000C R, L Part ID Clock part family ID[7:0] 01
0x000D R, L Clock part family ID[15:8] 00
System Clock
0x0100
SYSCLK
config PLL
feedback
divider
System clock N divider[7:0] 08
0x0101 Reserved
Load from
ROM (read
only)
SYSCLK
XTAL
enable
SYSCLK P divider[1:0]
SYSCLK
doubler
enable
09
or
19
0x0102 Reserved Reserved 00
0x0103
SYSCLK
period
Nominal system clock period (fs)[7:0] (1 ns at 1 ppm accuracy) 0E
0x0104 Nominal system clock period (fs)[15:8] (1 ns at 1 ppm accuracy) 67
0x0105 Reserved Nominal system clock period[20:16] 13
0x0106
SYSCLK
stability
System clock stability period (ms)[7:0] 32
0x0107 System clock stability period (ms)[15:8] 00
0x0108 A Reserved
Reset
SYSCLK stab
timer
(autoclear)
System clock stability period (ms)[19:16]
(not autoclearing)
00
General Configuration
0x0200 EN_MPIN Reserved
Enable M
pins and
IRQ pin
function
00
0x0201 M0FUNC
M0 output/
A
input
E
Function[6:0] B0
0x0202 M1FUNC
M1output/A
input
E
Function[6:0] B1
0x0203 M2FUNC
M2 output/
A
input
E
Function[6:0] C0
0x0204 M3FUNC
M3 output/
A
input
E
Function[6:0] C1
0x0205 Reserved B2
0x0206 Reserved B3
0x0207 Reserved C2
0x0208 Reserved C3