Data Sheet
UM10204 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
User manual Rev. 6 — 4 April 2014 43 of 64
NXP Semiconductors
UM10204
I
2
C-bus specification and user manual
opens to separate the two bus sections and allows Hs-mode devices to communicate with
each other at 3.4 Mbit/s. Arbitration between Hs-mode devices and F/S-mode devices is
only performed during the master code (0000 1XXX), and normally won by one Hs-mode
master as no slave address has four leading zeros. Other masters can win the arbitration
only if they send a reserved 8-bit code (0000 0XXX). In such cases, the bridge remains
closed and the transfer proceeds in F/S-mode. Table 8
gives the possible communication
speeds in such a system.
Remark: Table 8 assumes that the Hs devices are isolated from the Fm and Sm devices
when operating at 3.4 Mbit/s. The bus speed is always constrained to the maximum
communication rate of the slowest device attached to the bus.
(1) Bridge not used. SDA and SCL may have an alternative function.
(2) To input filter.
(3) Only the active master can enable its current-source pull-up circuit.
(4) Dotted transistors are optional open-drain outputs which can stretch the serial clock signal SCL or SCLH.
Fig 36. Bus system with transfer at Hs-mode and F/S-mode speeds
msc614
V
SS
Hs-mode
SLAVE
SDAH SCLH
V
SS
Hs-mode
MASTER/SLAVE
SDAH SCLH SDA SCL
R
s
R
s
Hs-mode
SLAVE
SDAH SCLH
V
SS
R
s
R
s
F/S-mode
MASTER/SLAVE
SDA
SDAH
SCLH
SDA
SCL
SCL
V
SS
V
SS
R
s
R
s
F/S-mode
SLAVE
SDA SCL
V
SS
R
s
R
s
R
s
R
s
R
s
R
s
V
DD
V
SS
Hs-mode
MASTER/SLAVE
V
DD
V
DD1
R
p
R
p
V
DD2
R
p
R
p
SCLH
SDAH
MCSMCS
(3)
(3)
(2)(2) (2)(2) (2)(2) (2)(2)(2)(2)(2)
(4) (4) (4)
(2)
(1) (1)
BRIDGE
TR1
TR3
TR2
Table 8. Communication bit rates in a mixed-speed bus system
Transfer between Serial bus system configuration
Hs + Fast +
Standard
Hs + Fast Hs + Standard Fast + Standard
Hs ↔ Hs 0 to 3.4 Mbit/s 0 to 3.4 Mbit/s 0 to 3.4 Mbit/s -
Hs ↔ Fast 0 to 100 kbit/s 0 to 400 kbit/s - -
Hs ↔ Standard 0 to 100 kbit/s - 0 to 100 kbit/s -
Fast ↔ Standard 0 to 100 kbit/s - - 0 to 100 kbit/s
Fast ↔ Fast 0 to 100 kbit/s 0 to 400 kbit/s - 0 to 100 kbit/s
Standard ↔ Standard 0 to 100 kbit/s - 0 to 100 kbit/s 0 to 100 kbit/s