ez80f91 ZiLOG Semiconductor, ez80f91 Datasheet - Page 245

• Manufacturer Part Number: ez80f91
• Description: Ez80 Acclaimplus!? Connectivity Assp Ez80f91 Assp
• Manufacturer: ZiLOG Semiconductor

PS027001-0707
ZDI Clock and Data Conventions
ZDI START Condition
The two pins used for communication with the ZDI block are the ZDI clock pin (ZCL) and
the ZDI data pin (ZDA). On eZ80F91, the ZCL pin is shared with the TCK pin while the
ZDA pin is shared with the TDI pin. The ZCL and ZDA pin functions are only available
when the On-Chip Instrumentation is disabled and the ZDI is therefore enabled. For gen-
eral data communication, the data value on the ZDA pin changes only when ZCL is Low
(0). The only exception is the ZDI START bit, which is indicated by a High-to-Low transi-
tion (falling edge) on the ZDA pin while ZCL is High.
Data is shifted into and out of ZDI, with the most-significant bit (bit 7) of each byte being
first in time, and the least-significant bit (bit 0) last in time. All information is passed
between the master and the slave in 8-bit (single-byte) units. Each byte is transferred with
nine clock cycles; eight to shift the data, and the ninth for internal operations.
All ZDI commands are preceded by the ZDI START signal, which is a High-to-Low tran-
sition of ZDA when ZCL is High. The ZDI slave on the eZ80F91 device continually mon-
itors the ZDA and ZCL lines for the START signal and does not respond to any command
until this condition is met. The master pulls ZDA Low, with ZCL High, to indicate the
beginning of a data transfer with the ZDI block.
trates a valid ZDI START signal prior to writing and reading data, respectively. A Low-to-
High transition of ZDA while the ZCL is High produces no effect.
Figure 49. Schematic For Building a Target Board ZPAK Connector
eZ80F91
TCK (ZCL)
TDI (ZDA)
10 Kohm
6-Pin Target Connector
10 Kohm
Figure 50
and
Figure
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4
6
Product Specification
51on page 238 illus-
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5
Zilog Debug Interface
eZ80F91 ASSP
(Target V
TV
DD
DD
)
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