Texas Instruments Digital Signal Processor SM320F2812-HT - Manual (Page 128)

SM320F2812-HT
SGUS062B – JUNE 2009 – REVISED JUNE 2011 www.ti.com
6.27 XHOLD and XHOLDA
f the HOLD mode bit is set while XHOLD and XHOLDA are both low (external bus accesses granted), the
XHOLDA signal is forced high (at the end of the current cycle) and the external interface is taken out of
high-impedance mode.
On a reset (XRS), the HOLD mode bit is set to 0. If the XHOLD signal is active low on a system reset, the
bus and all signal strobes must be in high-impedance mode, and the XHOLDA signal is also driven active
low.
When HOLD mode is enabled and XHOLDA is active low (external bus grant active), the CPU can still
execute code from internal memory. If an access is made to the external interface, the CPU is stalled until
the XHOLD signal is removed.
An external DMA request, when granted, places the following signals in a high-impedance mode:
XA[18:0] XZCS0AND1
XD[15:0] XZCS2
XWE, XRD XZCS6AND7
XR/W
All other signals not listed in this group remain in their default or functional operational modes during these
signal events. Detailed timing diagram is released in a future revision of this data sheet.
128 Electrical Specifications Copyright © 2009 – 2011, Texas Instruments Incorporated
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