EZ80F920120MOD Zilog, EZ80F920120MOD Datasheet - Page 182

• Manufacturer Part Number: EZ80F920120MOD
• Description: MODULE EZ80F92 512K 20MHZ
• Manufacturer: Zilog

Specifications of EZ80F920120MOD

• Module/board Type: Development Module
• Processor Series: EZ80F92x
• Core: eZ80
• Data Bus Width: 8 bit
• Program Memory Type: Flash
• Program Memory Size: 1 MB
• Interface Type: Cable
• Maximum Clock Frequency: 20 MHz
• Operating Supply Voltage: 0 V to 3.3 V
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• Package / Case: LQFP
• Development Tools By Supplier: eZ80F920200ZCOG
• Minimum Operating Temperature: 0 C
• For Use With/related Products: eZ80F92
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 269-3157; EZ80F920120MOD

eZ80F92/eZ80F93
Product Specification
170
When using the ZDI interface, any Write or Read operations of peripheral registers in the
I/O address space produces the same effect as Read or Write operations using the CPU.
Because many register Read/Write operations exhibit secondary effects, such as clearing
flags or causing operations to commence, the effects of the Read/Write operations during a
ZDI BREAK must be taken into consideration.
Bus Requests During ZDI DEBUG Mode
The ZDI block on the eZ80F92 device allows an external device to take control of the
address and data bus while the eZ80F92 device is in DEBUG mode. ZDI_BUSACK_EN
causes ZDI to allow or prevent acknowledgement of bus requests by external peripherals.
The bus acknowledge only occurs at the end of the current ZDI operation (indicated by a
High during the single-bit byte separator). The default reset condition is for bus acknowl-
edgement to be disabled. To allow bus acknowledgement, the ZDI_BUSACK_EN must be
written.
When an external bus request (BUSREQ pin asserted) is detected, ZDI waits until comple-
tion of the current operation before responding. ZDI acknowledges the bus request by
asserting the bus acknowledge (BUSACK) signal. If the ZDI block is not currently shift-
ing data, it acknowledges the bus request immediately. ZDI uses the single-bit byte separa-
tor of each data word to determine if it is at the end of a ZDI operation. If the bit is a
logical 0, ZDI does not assert BUSACK to allow additional data Read or Write operations.
If the bit is a logical 1, indicating completion of the ZDI commands, BUSACK is asserted.
Potential Hazards of Enabling Bus Requests During DEBUG Mode
There are some potential hazards that the user must be aware of when enabling external
bus requests during ZDI DEBUG mode. First, when the address and data bus are being
used by an external source, ZDI must only access ZDI registers and internal CPU registers
to prevent possible Bus contention. The bus acknowledge status is reported in the
ZDI_BUS_STAT register. The BUSACK output pin also indicates the bus acknowledge
state.
A second hazard is that when a bus acknowledge is granted, the ZDI is subject to any
WAIT states that are assigned to the device currently being accessed by the external
peripheral. To prevent data errors, ZDI should avoid data transmission while another
device is controlling the bus.
Finally, exiting ZDI DEBUG mode while an external peripheral controls the address and
data buses, as indicated by BUSACK assertion, may produce unpredictable results.
PS015308-0404
P R E L I M I N A R Y
ZiLOG Debug Interface