DS2154
10 CLOCK BLOCKING REGISTERS
The Receive Channel Blocking Registers (RCBR1/RCBR2/RCBR3/RCBR4) and the Transmit Channel
Blocking Registers (TCBR1/TCBR2/TCBR3/TCBR4) control the RCHBLK and TCHBLK pins,
respectively. The RCHBLK and TCHCLK pins are user-programmable outputs that can be forced either
high or low during individual channels. These outputs can be used to block clocks to a USART or LAPD
controller in ISDN-PRI applications. When the appropriate bits are set to 1, the RCHBLK and TCHCLK
pins will be held high during the entire corresponding channel time. See the timing diagrams in Section
14 for an example. The TCBRs have alternate mode of use. Via the CCR3.6 bit, the user has the option to
use the TCBRs to determine, on a channel-by-channel basis, which signaling bits are to be inserted via
the TSRs (the corresponding bit in the TCBRs = 1) and which are to be sourced from the TSER or TSIG
pins (the corresponding bit in the TCBR = 0). See Section 8 for more details about this mode of
operation.
RCBR1/RCBR2/RCBR3/RCBR4: RECEIVE CHANNEL BLOCKING
REGISTERS (Address = 2B to 2E Hex)
(MSB)
CH8
CH16
CH24
CH32
(LSB)
CH1
CH7
CH15
CH23
CH31
CH6
CH14
CH22
CH30
CH5
CH13
CH21
CH29
CH4
CH12
CH20
CH28
CH3
CH11
CH19
CH27
CH2
CH10
CH18
CH26
RCBR1 (2B)
RCBR2 (2C)
RCBR3 (2D)
RCBR4 (2E)
CH9
CH17
CH25
SYMBOL
POSITION
NAME AND DESCRIPTION
CH32
CH1
RCBR4.7
Receive Channel Blocking Registers.
0 = force the RCHBLK pin to remain low during this channel
time
RCBR1.0
1 = force the RCHBLK pin high during this channel time
TCBR1/TCBR2/TCBR3/TCBR4: TRANSMIT CHANNEL BLOCKING
REGISTERS (Address = 22 to 25 Hex)
(MSB)
CH8
CH16
CH24
CH32
(LSB)
CH7
CH15
CH23
CH31
CH6
CH14
CH22
CH30
CH5
CH13
CH21
CH29
CH4
CH12
CH20
CH28
CH3
CH11
CH19
CH27
CH2
CH10
CH18
CH26
CH1
TCBR1 (22)
TCBR1 (23)
TCBR1 (24)
TCBR4 (25)
CH9
CH17
CH25
SYMBOL
POSITION NAME AND DESCRIPTION
CH32
TCBR4.7
Transmit Channel Blocking Registers.
0 = force the TCHBLK pin to remain low during this channel
time
CH1
TCBR1.0
1 = force the TCHBLK pin high during this channel time
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ROCHESTER [ Rochester Electronics ]
