
PSB 7280
Semiconductor Group
56
Data Sheet 1998-07-01
Receiver in LMOD(1:0) = 01, 10, 11
In receive direction, when the shift register from the serial line is filled to a programmable
level (1, 2 or 4), the whole 32-bit shift register is loaded into the HRR1/2 read registers,
physically separate for DSP and host. In the same cycle the contents of the HRW1/2
write register accessible from the DSP (if HHR1/2 = 0) or host (HHR1/2 = 1) are loaded
to the HDLC receiver input. In the next cycle the data from HRR1/2 is as a default loaded
into HRW1/2 and a maskable interrupt status BFHR1/2 is generated to the DSP and
host. The interrupt status is generated to both DSP and host, independent of the setting
of HAH1/2. If the data in HRR1/2 is to be pre-processed, the HRW1/2 register can be
overwritten by the DSP or host before the next 1, 2 or 4 bytes (programmable) have been
shifted into the shift register.
After reset (RRES) when starting the receiver (RAC = 1), the reset status data of HRW
and HRR is ignored by the receiver, i.e. the contents of HRW1/2 and HRR1/2 are not
forwarded to the HDLC receiver, but only the data received from the line. The same
applies to the interrupts: A BFHR1/2 interrupt is only generated after the first 1, 2 or
4 bytes of line data are available in the HRR1/2 register. Due to this pipeline, a latency
occurs in the HDLC/transparent serial data reception, see section below.
The start of the reception can be in the same frame (w.r.t. the frame sync signal on the
chosen line) as the setting of RAC = 1 since the time-slot count logic works
independently of RAC.
In transparent mode (TMO = 1) the reception is only started at the beginning of the time-
slot (time-slot aligned). If RAC is set to ‘1’ during the selected time-slot, the receiver waits
for the beginning of the time-slot in the next frame.
Receiver in LMOD(1:0) = 00
The same applies for LMOD = 00, except the pre-processing is not available. The data
from the bit-reversal unit is bypassed to the HDLC receiver. In addition, the loading of
HRR1/2, HRW1/2 and the generation of the interrupt BFHR1/2 is done like in the other
LMODs for observation of the data stream by the DSP or host only. Thus, the
LMOD = 00 is identical with LMOD = 01, except pre-processing is not available and the
receiver latency after reset is shortened, see section below.
Transmitter in LMOD(1:0) = 01, 10, 11
Similarly, in the transmit direction, after 1, 2 or 4 bytes (programmable) are shifted out of
the shift register, the contents of the HXW1/2 write register accessible from DSP
(if HHX1/2 = 0) or host (if HHX1/2 = 1) are loaded into the transmitter shift register. In the
same cycle 1, 2 or 4 bytes are loaded from the HDLC transmitter output into the HXR1/2
read register, physically separate for DSP and host. In the next cycle the data from
HXR1/2 is as a default loaded into HXW1/2 and a maskable interrupt status is generated
to the DSP and host. The interrupt status is generated to both DSP and host,
independent of the setting of HAH1/2. If the data in HXR1/2 is to be post-processed, the