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Philips Semiconductors
ISP1122
USB stand-alone hub
Product specification Rev. 03 — 29 March 2000 21 of 48
9397 750 07002
© Philips Electronics N.V. 2000. All rights reserved.
10.2 Hardware connections
Via the I
2
C-bus interface the ISP1122 can be connected to an external EEPROM
(PCF8582 or equivalent). The hardware connections are shown in Figure 5.
The SCL and SDA pins are multiplexed with pins OPTION and INDV respectively.
The slave address which ISP1122 uses to access the EEPROM is 1010000B. Page
mode addressing is not supported, so pins A0, A1 and A2 of the EEPROM must be
connected to GND (logic 0).
10.3 Data transfer
When the ISP1122 is reset, the I
2
C-bus interface tries to read 6 bytes of configuration
data from an external EEPROM. If no response is detected, the levels on inputs SDA
and SCL are interpreted as INDV and OPTION to select the operating mode (see
Table 4).
The data in the EEPROM memory are organized as shown in Table 22.
[1] Vendor ID code in the Device descriptor, see Table 10.
[2] Product ID code in the Device descriptor, see Table 10.
Fig 5. EEPROM connection diagram.
i
dth
MGR780
INDV/SDA
OPTION/SCL
A1
A2
A0
SDA
SCL
V
DD
R
P
R
P
V
DD
ISP1122
USB HUB
PCF8582
EEPROM
or
equivalent
I
2
C-bus
Table 22: EEPROM organization
Address
(Hex)
Default value
(Hex)
Contents
00 CC idVendor
[1]
(lower byte)
01 04 idVendor
[1]
(upper byte)
02 22 idProduct
[2]
(lower byte)
03 11 idProduct
[2]
(upper byte)
04 - configuration bits C7 to C0; see Table 23
05 AA signature