Host Data Strobe Mode (Hdsm) Bit 13; Host Read/Write Polarity (Hrwp) Bit 14 - Motorola DSP56305 User Manual

HOST INTERFACE (HI32)
DSP SIDE Programming Model
6.5.1.6

Host Data Strobe Mode (HDSM) Bit 13

The HDSM bit controls the data strobe mode of the host port signals when in a Universal
Bus mode (HM[2:0] is 010 or 011). If HDSM is cleared, the double-strobe signal mode is
selected: HWR/HRW signal (HP29) functions as host write strobe HWR and HRD/HDS
(HP30) functions as host read strobe HRD. If HDSM is set, the single-strobe signal mode
is selected: HWR/HRW signal functions as host read/write HRW and HRD/HDS
functions as host data strobe HDS.
The value of HDSM may be changed only when HACT (DSR Bit 23) is cleared.
HDSM is ignored when not in a Universal Bus mode (HM[2:0] is 010 or 011).
Hardware and software resets clear HDSM.
6.5.1.7

Host Read/Write Polarity (HRWP) Bit 14

The HRWP bit controls the polarity of HWR/HRW signal, when in single-strobe
Universal Bus modes (HM[2:0] is 010 or 011 and HDSM = 1), that is, when HWR/HRW
signal (HP29) functions as the host read/write (HRW) signal.
If HRWP is cleared, the host-to-DSP data transfer direction corresponds to low level of
HRW signal, and DSP-to-host data transfer direction corresponds to high level of HRW
signal.
If HRWP is set, the host-to-DSP data transfer direction corresponds to high level of HRW
signal, and DSP-to-host data transfer direction corresponds to low level of HRW signal.
The value of HRWP may be changed only when HACT = 0.
HRWP is ignored when not in a Universal Bus mode or double-strobe host port mode is
≠
selected (HM $2 or $3, or HDSM = 0).
Hardware and software resets clear HRWP.
6-14 DSP56305 User's Manual MOTOROLA